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There are three different ways that Tannaim derive the source for wearing tefillin on the left hand. However, left-handed people wear them on the right. There are three different ways that Tannaim derive the source for wearing tefillin shel yad on the upper part of the arm. There are two different ways that Tannaim derive the source for wearing tefillin shel rosh on the top of the head. There is a Tannatic debate between Rabbi Yishmael and the rabbis about whether each tzitzit is a distinct mitzva (Rabbi Yishmael), or if one cannot fulfill the mitzva without having tzitzit on all four corners. The Gemara brings three practical ramifications of their debate. There are three examples brought of changes one can make to a four-cornered garment which, while it may no longer look like a four-cornered garment, would still be obligated in tzitzit. Shmuel ruled like Rabbi Yishmael, but the Gemara states that the halakha is not like that and brings a story with Mar bar Rav Ashi and Ravina to prove it.

Rav Chisda explains that if one speaks between placing the tefillin shel yad and the tefillin shel rosh, an additional blessing must be recited upon the shel rosh. From this, one can infer that if no interruption occurs, only one blessing is required. However, this poses a difficulty in light of Rabbi Yochanan's statement that there are separate blessings for the shel yad and shel rosh. Abaye and Rava resolve this conflict, yet their resolution is interpreted differently by Rashi and Rabbeinu Tam, resulting in two distinct customs. The tefillin shel yad is placed first, followed by the shel rosh. When removing them, the order is reversed: the shel rosh is removed first, then the shel yad. This specific sequence is derived from the verse in Devarim 6:8. If one dons tefillin early in the morning before the proper time has arrived, the blessing is recited the moment the obligation begins. As stated in Berakhot 9b, this occurs when it becomes light enough to recognize an acquaintance from a distance of four cubits. There are three opinions regarding how late one may wear tefillin: until sunset, until the last people leave the market, or until one goes to sleep. Two versions of Rav Nachman's ruling exist - either supporting or opposing the middle position. This ruling either aligns with or contradicts the practice of Rav Chisda and Raba bar Rav Huna, who would pray Maariv while still wearing tefillin. A challenge is raised against Raba bar Rav Huna's practice based on his own statement implying that tefillin must be removed as darkness falls. This is resolved by explaining that his statement referred specifically to Shabbat. There are two different derivations for the exemption of tefillin on Shabbat: one links it to the exemption of wearing tefillin at night, while the other does not. Is it forbidden to don tefillin at night? If so, does one transgress a positive commandment or a negative one? One should touch the tefillin while wearing them to maintain constant awareness of them. This is derived via a kal v'chomer (a fortiori argument) from the tzitz (the Kohen Gadol's forehead plate). Tefillin are worn on the left hand, as derived from various verses indicating that the word "yad" refers specifically to the left hand.

Pictures The exact order of the four biblical passages (parshiot) within the tefillin shel rosh is critical; if they are not arranged in their specific sequence, the tefillin are disqualified. Abaye and Rava debate the specifics of this requirement, questioning the validity of the tefillin if the two "outer" sections (the first and last) or the two "inner" sections are transposed. Several physical elements of the tefillin are classified as halakha l'Moshe m'Sinai: the embossed letter Shin on the Shel Rosh, the requirement for the boxes to be perfectly square, the titura (the base), and the ma'abarta (the passageway for the straps). Regarding the straps (retsuot), the outer side must be black. The underside may be other colors, though red is strictly prohibited. If a strap is partially torn, it is disqualified. The Gemara distinguishes this from tzitzit or a hyssop branch, where "remnants" may still be valid; this is because tefillin straps serve an object of inherent kedusha (sanctity), requiring a higher standard. The knot of the shel rosh must be shaped like the letter dalet (halakha l'Moshe m'Sinai). Rav Nachman rules that the knot should be prominent and face outward, reflecting the idea that tefillin serve as a sign to the nations that "God's name is called upon you." This purpose also dictates the exact placement of the knot at the base of the skull and the box on the head. Finally, the blessing is recited after the tefillin are placed but before the final wrapping or tightening is completed.

Rav Huna states that a closed-in staircase opening (lul) between a house and an upper story requires one mezuza if it has one entrance and two mezuzot if it has two. Rav Papa infers from this that a room (indrona) with four doors requires four mezuzot, even if the resident typically utilizes only one of them. Amemar rules that a doorway situated at a corner is obligated in a mezuza; though Rav Ashi questions this due to the lack of formal doorposts (patzim), Amemar maintains that the edges of the walls themselves serve as the post. Rav Papa observes a doorway in Mar Shmuel's house that had only a left-side post yet was fitted with a mezuza. He questions this practice, as it seems to follow Rabbi Meir, who obligates a mezuza for a house with only one post—but even Rabbi Meir only holds that a mezuza is placed on the right side. The source for the right-side placement is derived from the word "beitecha" (your house), which is interpreted as "biatcha" (your entry). The connection between entry and the right side is either because a person begins their entry by leading with the right foot, or it is derived from the verse regarding Jehoiada the kohen, who placed a chest for donations to the right of the altar as people "came in." The dispute between Rabbi Meir and the Rabbis regarding a single doorpost centers on the plural phrasing of "mezuzot." The Rabbis hold this implies a minimum of two posts, while Rabbi Meir explains how the term can signify a single post, based on the interpretations of Rabbi Yishmael and Rabbi Akiva who utilize various exegetical principles. A braita derives the obligation to write the mezuza on parchment and then affix it to the wall, rather than writing it directly on the stones of the doorpost as might be understood from a simple reading of the verse. Regarding tefillin, the four paragraphs are all essential (me'akvot); even the omission of a single letter, or the "tip" of the letter yud, renders them invalid. Rav Yehuda in the name of Rav adds that every letter must be surrounded by blank parchment on all four sides. The Gemara discusses the source for the four compartments of the head tefillin (shel rosh). Rabbi Yishmael derives the number four from the number of mentions and spelling variations of the word "totafot," while Rabbi Akiva explains that the word is a compound of "tat" (two in the Katpi language) and "pat" (two in the Afriki language). A braita clarifies that while the tefillin shel rosh contain four separate scrolls in four compartments, the arm tefillin (shel yad) consist of all four paragraphs written on a single scroll. If one wrote the tefillin shel rosh on one scroll, it is valid, as long as it is put into four separate compartments. If one wrote the tefillin shel yad on four separate scrolls and placed them in one compartment, it is valid, though Rabbi Yehuda requires them to be glued together to appear as one. Rabbi Yosi rules that a tefillin shel rosh can be used on the arm if it is covering by one piece of leather. A contradiction is raised against Rabbi Yosi as Rabbi Yochanan ruled that this is not possible as one cannot lower an item in sanctity, i.e. from the head to the arm. The order of the paragraphs to be placed in the four compartments of the tefillin shel rosh is established as: kadesh and v'haya ki yeviacha on the right, followed by shema and v'haya im shamoa on the left. To resolve a contradiction with another source that reverses this, Abaye clarifies that each source refers to a different perspective of "right" and "left," depending on whether one is looking from the perspective of the reader or the wearer. Rashi and Rabbeinu Tam (among others) disagree about how to understand the specific order of the tefillin described in the Gemara. Rav concludes that if a scribe switches the order of the paragraphs, the tefillin are invalid.

Rav Yehuda in the name of Shmuel rules that a mezuza written on two sheets or columns is invalid. The Gemara raises a difficulty from a braita that invalidates a mezuza written on two sheets only when it is placed within two separate sippin (doorposts), implying that if it were placed within a single post, it would be valid. The difficulty is resolved by explaining that Shmuel's intent was that even if it is placed in one post, the mere fact that it is "fit" or able to be divided between two posts renders it invalid, as a mezuza. Regarding the determination of the right side in doorways between two rooms, Shmuel rules that one follows the "heker tzir" (the placement of the hinges). Rav Adda explains that this refers to the socket in which the door hinge turns; the side toward which the door opens is considered the primary room, and the right side is determined according to the direction of entry into that room. Rav Nachman instructed the Exilarch (Resh Galuta), who wished to fix a mezuza in his house before its construction was complete, that he must first hang the doors and only afterward fix the mezuza. Concerning the manner of placing the mezuza, Rav Yehuda in the name of Rav invalidates a mezuza placed "k'min neger" (like a bolt), meaning like a horizontal bar inserted into the doorway. The Gemara raises a difficulty from the practice in Rabbi's house, where the mezuzot were placed "k'min neger," and resolves it by distinguishing between a completely vertical placement and a horizontal placement. It is further mentioned in this context that Rav Huna would fix a mezuza in the doorway between his house and the Beit Midrash even though Rabbi did not do so, because Rav Huna followed the practice of those accustomed to using that doorway, which renders it a doorway obligated in a mezuza. In the matter of the mezuza's height, Shmuel rules that it should be placed at the beginning of the upper third of the doorway's height. Rav Huna disagrees, holding that the entire area of the doorway is valid, provided the mezuza is one handbreadth (tefach) away from the ground and one handbreadth away from the ceiling beam. The Gemara raises a difficulty against Shmuel from a braita and resolves it by explaining that Shmuel rules in accordance with Rabbi Yosi, who learns from a hekesh (textual comparison) between "u'kshartam" (tefillin) and "u'khtavtam" (mezuza) that just as tefillin are placed high up, so too the mezuza must be high up in the doorway. Rava adds that the mezuza should be placed in the handbreadth closest to the public domain so that a person encounters the mitzva immediately upon entry. Rabbi Chanina adds a conceptual dimension: unlike a king of flesh and blood who sits inside while his subjects guard him from the outside, God guards His servants from the outside while they sit inside, as it is written, "The Lord is your guardian." Additional laws discussed on this page deal with the requirements of a mezuza that depend on the structure of the doorway and the room. Rav Yosef in the name of Rava invalidates a mezuza that was recessed into the thickness of the wall more than a handbreadth. Rava exempts "pitchi shimai" (defective doorways) from mezuza; the Amoraim dispute whether this refers to a doorway without a ceiling or one without a proper doorpost. Similarly, an achsadra (portico) is exempt from mezuza because its posts are intended to support the ceiling rather than to create a doorway. A gatehouse (beit shaar) that opens both to a house and a courtyard needs a mezeua on both entrances. However, a gatehouse that opens to both a house and a garden, the Tannaim dispute - and the Amoraim dispute the interpretation of their words - whether the obligation is determined by the entry to the house or the exit to the garden. Rav Ashi rules according to the stringency of Rav and Shmuel: any doorway used for entry into a house, even if it leads to an open space like a garden, is obligated in a mezuza.  

Rav Chelbo relates that he saw Rav Huna roll the mezuza from the word "echad" toward the word "shema" and format the paragraphs as setumot (closed). This practice is questioned by a braita where Rabbi Shimon ben Elazar notes that Rabbi Meir wrote mezuzot on duchsustos with margins at the top and bottom and formatted the paragraphs as petuchot (open). Rabbi Meir's reasoning was that the paragraphs are not adjacent in the Torah text itself. Since Rav (Rav Huna's teacher) rules in accordance with Rabbi Shimon ben Elazar, that raises a difficulty on Rav Huna's practice. To resolve the difficulty, it is suggested that Rav only ruled like Rabbi Shimon ben Elazar regarding the margins. Abaye further supports this resolution by showing that Rav gives weight to local custom, and the established custom is to write them setumot. The Gemara brings an example to show that Rav gave weight to the established custom from a statement he made regarding use of a sandal for chalitzah, noting that even the testimony of the prophet Eliyahu would not overturn a practice the people have already adopted to use a sandal. Rav Nachman bar Yitzchak offers an alternative explanation for the difficulty on Rav Huna. He explains Rabbi Shimon ben Elazar's position as being that while it is a mitzva (ideal) to make them setumot, if they were written petuchot, it would be valid; he reads the words in the braita as "even petuchot." Support for Rav Nachman is brought from a braita stating that a worn-out Sefer Torah or tefillin cannot be repurposed into a mezuza because one does not "lower" an object from a higher level of sanctity to a lower one. From the reason given in the braita, one can infer that if it were not a matter of "lowering" in sanctity, it could be repurposed. This would prove that setumot could be used, as those sections are setumot in a Sefer Torah. However, this suggested proof is rejected. The Gemara raises two other difficulties on the inference that, but for the issue of "lowering" sanctity, a Sefer Torah or tefillin could be repurposed for a mezuza. The first is that tefillin are written on klaf on the side facing the flesh, while a mezuza is written on duchsustos on the side facing the hair. The second difficulty is that a mezuza requires lines (sirtut), while tefillin do not. Both difficulties are resolved. Rav Chelbo further observes that Rav Huna would not sit on a bed while a Sefer Torah was resting upon it, opting instead to place the Torah on an inverted vessel on the ground. However, Rabba bar bar Hana, quoting Rabbi Yochanan, permits sitting on the same bed as a Torah. Rav Yehuda in the name of Shmuel states that a mezuza written in a "letter" (iggeret) format is invalid, as it requires the formal writing style of a Sefer. He also rules that hanging a mezuza on a stick or placing it behind a door is invalid and even "dangerous," as it must be fixed "on your gates." Shmuel specifies that the mezuza must be placed within the hollow of the doorway.

Ravin, the son of Chinina, said in the name of Ulla in the name of Rabbi Chanina that the law follows Rabbi Shimon Shezuri in "this" issue and anywhere else he issued a ruling. Rav Papa and Rav Nachman bar Yitzchak each identify a possible case where Rabbi Chanina ruled like Rabbi Shimon Shezuri. One suggests it was regarding how to measure 40 se'ah in a large box for purposes of impurity. The other suggests it was regarding the stringent ruling of the impurity of liquids - specifically, to which liquids this unique type of impurity extends. The Gemara brings a situation where Rabbi Shimon Shezuri mixed untithed produce with tithed produce and was told by Rabbi Tarfon to buy produce from the market to tithe upon it. In a different version, Rabbi Tarfon told him to buy produce from non-Jews. This advice is analyzed through two lenses: whether a market purchase is considered tithed by Torah law because most am ha'aretz tithe, or whether land ownership by non-Jews in Israel removes the Torah obligation of tithing the produce. Rav Papa confirms to Rav Yemar bar Shelamya that the halakha follows Rabbi Shimon Shezuri even in this specific case. A statement by Rav regarding a tear in the parchment of a Sefer Torah is also analyzed. Rav rules that a tear spanning two lines may be sewn, but a tear of three lines may not. This is qualified by Rabba Zuti, who distinguished between "new" and "old" parchment, which is defined not by age but by whether or not it was processed with gall. Furthermore, the sewing must be done with sinews (gidin) and not plain thread. A question is left unresolved regarding whether these measurements apply if the tear occurs between columns or between lines. Regarding the writing of a mezuza, Rav Chananel in the name of Rav states that if it is written with two words on a line, it is valid. Rav Nachman explains that it can be written like a shira (song) - for example, two words, then three, then one. When questioned by a braita, he distinguishes between the requirements of a Sefer Torah and a mezuza. The Gemara clarifies that while a mezuza can be written in shira format, it must not be formatted like a "tent" or a "tail" (narrowing or widening). There is a discussion regarding the final words of the mezuza, "al ha'aretz." Should they be placed at the end of the line or at the beginning? The two views reflect different symbolic meanings: one highlights the height of heaven above the earth, while the other highlights the distance between them. Rav Chelbo mentions Rav Huna, who would roll the mezuza scroll from the end to the beginning and made the paragraphs "closed" (setumot). This is challenged by a ruling of Rabbi Meir, who made the paragraph breaks "open" (petuchot).

Rav makes a statement that is contradicted by a braita. He says that the last page of a Sefer Torah can end in the middle of the page, while a braita says it must finish at the end. After trying to reconcile Rav's position with the braita by limiting it to a Chumash (a parchment containing only one book of the Torah) and not a full Sefer Torah, the Gemara questions this from another statement of Rav (brought by Rabbi Yehoshua bar Aba in the name of Rav Gidal). There are two versions of the explanation for Rav's second statement, which may affect whether his position can be reconciled with the braita and whether one needs or is permitted to finish the last line of the Torah in the middle of the line. Two other statements of Rabbi Yehoshua bar Aba in the name of Rav Gidal in the name of Rav are brought regarding the Torah. The first discusses a specific rule regarding the last eight verses of the Torah describing Moshe's death: an individual reads them in a shul. There is a debate among the commentaries regarding the meaning of this rule. Initially, it is suggested that this rule follows the view that Yehoshua wrote these verses, but the Gemara concludes it can also be explained according to Rabbi Shimon, who held that Moshe wrote them b'dema. The second statement is that one who buys a Sefer Torah in the market does not fulfill the mitzva in the proper manner, as ideally one should write a Sefer Torah rather than buy it. A piece of parchment used in a Sefer Torah can contain between three and eight columns. A column should include approximately 30 letters. However, there are different rules regarding the last page of the Torah. How many letters can be added in the margin if needed, and under what circumstances? If one omits the name of God, how can this be fixed? There are five tannaitic opinions, ranging from no solution to scraping the ink of a different word and inserting God's name there (placing the other word between the lines) to even allowing half the name of God to be added between the lines. Rabbi Shimon Shezuri's opinion is that the name of God can be added between the lines, but only if it is the whole name. Ravin son of Chinina said in the name of Ulla in the name of Rabbi Chanina that the law follows Rabbi Shimon Shezuri in "this" issue and anywhere else he issued a ruling. The Gemara tries to establish what "this" issue is. Each time a possibility is suggested, starting with our sugya,  it is rejected because others also issued rulings, and when the Gemara listed who ruled like whom, Ravin bar Chinina and rabbi Chanina did not appear there.

The Menora in the Temple featured various decorative parts, including goblets, knobs, and flowers. The Gemara details the quantity of each and their specific placement on the Menora. Rav explained that the Menora's height was nine handbreadths from the point where the lowest branches met. The text describes the gold used for the Menora as "michlot zahav." Rabbi Ami interpreted this phrase to mean that all the refined gold from King Solomon's era was used for its construction. Rabbi Shmuel bar Nachmani explained that the Menora is called "tehora" (pure) because it was shown to Moshe as a heavenly image. The Gemara explores why this same explanation is not applied to the "shulchan hatehora" (the pure table) used for the showbread; in that case, the phrase indicates that the table could potentially become impure. There were other items as well that God had to show Moshe, as they were difficult for him to grasp. The Mishna explains that the two parshiot (sections) in the mezuza are essential. Initially, it is assumed this refers to the small tip of the letter yud (kotzo shel yud), but this is rejected as being obvious. Instead, the Gemara suggests it serves to disqualify a mezuza if its letters are touching one another. Various rabbis discuss different issues regarding the letters hey and yud and whether or not certain formations disqualify them. Rav Yehuda says in the name of Rav that when Moshe went to receive the Torah, he found God attaching crowns to the letters. When Moshe asked why, God showed him Rabbi Akiva, who was extrapolating heaps of laws from every crown. Moshe was taken aback, as he did not understand Rabbi Akiva's teachings. However, once he heard Rabbi Akiva answer a student that a certain law was "a halakha given to Moshe at Sinai," Moshe was relieved. Yet, when he asked God what the reward would be for such a great scholar, God showed him Rabbi Akiva's tragic death, and Moshe was once again disturbed. In both instances, God told Moshe, "Be silent, for this is My decree." Seven specific letters are adorned with three crowns. There were also special requirements for writing the letters yud and chet, with explanations provided for each. The rabbis discuss in which situations mistakes in a Sefer Torah can be corrected and in which situations they cannot.

Study Guide There are two contradictory braitot regarding the oil of the leper that was sprinkled for the sake of the wrong sacrifice. One rules that it is disqualified, and the other rules that it is valid. At first, it was suggested that one matches the opinion of Rabbi Eliezer - who disqualifies a guilt offering (which the oil of the leper is brought with) that is brought with the wrong intent - but this suggestion is rejected. They conclude by saying that each relates to a different issue: the one that permits is referring to permitting the remainder of the oil to be eaten, while the one that disqualifies relates to the owner receiving purification. The Mishna discusses elements of the Menora, mezuza, tefillin, and tzitzit that are essential. In the Menora, the seven branches are essential. The Gemara brings a braita that explains other elements of the Menora that are essential. It must be made from one chunk of gold; however, while the "chunk" is essential, it could be made from metals other than gold if gold is unavailable. How is this derived from the verses? How does this differ from the trumpets? Rav Papa, son of Rav Chanin, brought a braita with a debate between two Tannaim about whether all other metals could be used or only silver. However, Rav Yosef brings an alternative braita stating that the debate was about wood, but all agree that all other metals can be used. Rav Yosef further proves from two other braitot that his version is correct. Shmuel quotes an elder who described the height of the Menora and what could be found at every level. He also listed how many of the decorative elements were to be found on the Menora and ruled that each one is an essential part of the Menora.

The Mishna lists different elements of the mincha and other offerings that are essential. The Gemara delves into the derivations for each of these. Some elements are repeated Torah, and this repetition serves as an indicator that the act must be performed in that specific way. Others are deemed essential due to a specific formulation in the verse - a word that indicates a particular detail is necessary. The Gemara delves into two specific issues related to items on the list. One involves the four species of the lulav. A statement of Rav Chanan bar Rava is brought—that the essential element of the four species is that they be present, but they do not all need to be taken at once. A difficulty is raised against him from a braita that makes clear that the species need to be bound together. This is resolved by explaining that there are two different Tannaitic positions on this, based on whether or not the species are required to be bound. The second issue is the sprinkling of the blood of the Red Heifer, which must be performed while facing the Sanctuary. There are two contradictory braitot: one holds that if the blood is not sprinkled while facing the Sanctuary, it is disqualified, while another holds that it is not. Two resolutions are brought - either each source reflects a different Tannaitic position, or each is addressing a different situation.

If the remainder of the mincha offering becomes impure, lost, or burned before the kometz is offered, according to Rabbi Eliezer and Rabbi Yehoshua's approaches regarding sacrifices, one can explain what they would each hold on whether the kometz may still be burned. In the case of animal sacrifices, Rabbi Eliezer permits the sprinkling of the blood even if there is no meat left, whereas Rabbi Yehoshua forbids it. Rav explains that Rabbi Yehoshua's restriction only applies if the entire remainder is lost; however, if even a portion remains, the kometz may be burned. This aligns with his view on animal sacrifices - that if even an olive-bulk of meat or sacrificial fats remains, the blood may be sprinkled. Does the kometz require a sacred vessel after being taken from the meal offering, or can it be brought by hand to the altar? Rabbi Shimon and the Sages differ on this requirement, with Rabbi Shimon ruling that a vessel is not required at this stage. The Gemara explores three different approaches to explain the underlying logic of Rabbi Shimon's lenient view, bringing braitot to challenge the different opinions. If the kometz is split into two parts, the Mishna rules that it can be burned in two separate actions. However, Rabbi Yochanan and Rabbi Yehoshua ben Levi disagree about whether it can be split into more than two parts. What is the basis of their debate? Rabbi Yochanan and Rabbi Chanina disagree about the exact point at which the burning of the kometz renders the remainder permitted for consumption.  

The tzitz (headplate of the Kohen Gadol) effects atonement only for the disqualification of impurity (tum'ah) and not for other disqualifications such as yotzei (sacrificial meat taken outside its boundaries), piggul (improper intent), notar (remnants left past the legal time), or ba'al mum (a blemished animal). Both in the braita and in the discussions of the amoraim, these laws are derived from the biblical verses - establishing that the tzitz atones specifically for impurity and not for other types of disqualifications. The Gemara highlights a contradiction between two braitot: one states that the tzitz atones for an individual's offering only if it occurred inadvertently (shogeg), while the other states that the tzitz atones whether it occurred inadvertently or intentionally (mezid). The Gemara offers four potential solutions to resolve this contradiction, the first of which is rejected.  

A Mishna in Chagigah 20b explains that sanctified items placed in the same sanctified vessel are considered combined for purposes of impurity; for example, if a tvul yom touched one, everything else in the vessel would become impure. However, this is only if they are all touching. The sons of Rabbi Chiya asked Rav Kahana if that would hold true even if they weren't touching. Rav Kahana derived from the word "tzeiruf" used in the Mishna there that they would combine. They ask two more related questions and Rav Kahana answers them. Then, Rav Kahana asks them a question about whether combining two items in a bowl, when not touching, would be valid for taking a kemitza (if the dough of the mincha was split into two parts). They attempted to make a comparison between the case in question and the case in our Mishna regarding the two minchas that got mixed together. However, Rava rejects the comparison as it is likely they were touching. Rabbi Yirmia asks a follow-up question about items being connected regarding impurity—in a case where the item is attached through water (in a pipe) to something outside of the vessel. Would the impurity extend to there as well? Or what if the outside piece became impure, would it extend to the other piece in the bowl as well? If a mincha offering was divided and one part became impure and was then added to a bowl with its other half, if a tvul yom then comes and touches the impure half while it is in the bowl with the other, is the other piece impure as well? This is in essence asking whether once something is impure, can impurity be added again? Rava asked this question and Abaye tried to answer it from a Mishna in Keilim 27:9, explaining that there is no such concept that once something is impure it cannot become impure again, but Rava rejects his proof as the cases aren't comparable. The Gemara further tries to prove Abaye's point from the continuation of that Mishna, but that is rejected as well. Rava and Abaye disagree about a case where there are three pieces—two from the original, one of which was lost temporarily, and a third that came to replace the lost half. What is the relationship between the three for laws of impurity and laws of kemitza?

Study Guide Rabbi Yochanan and Reish Lakish disagree about a case where oil was placed on the kometz of a mincha of a sinner, which is not meant to be mixed with oil. Rabbi Yochanan disqualifies it, but Reish Lakish does not, as he holds that the oil should not be mixed with the mincha before the kometz is taken, but the kometz can (and ideally should) be mixed with a little bit of oil. Rabbi Yochanan brings a tannaitic source to raise a difficulty against Reish Lakish's position, but it is resolved. Rava asks a question about a kometz whose oil (some of it) was absorbed onto a piece of wood. Can both be burned together to ensure that all the oil of the kometz is burned, or would this not be effective as the wood is completely separate from the kometz? Ravina questions Rava as the issue is already known as a debate between Rabbi Yochanan and Reish Lakish. But they explain why the question can be asked according to each. The Mishna explains what to do in three different cases of mixtures of meal offerings that were at various stages - either two minchas before the kometz was taken, or a kometz with a different mincha where the kometz was not yet taken, or a kometz mixed with the remainder. Rav Chisda and Rabbi Chanina disagree within Rabbi Yehuda's position of min b'mino (items of the same type) is not nullified, as understood by Rabbi Chiya, that items are considered the same if the status of one can change to be like the other. Rav Chisda says it is determined by the item trying to nullify, and Rabbi Chanina by the item being nullified. The three cases in our Mishna and a fourth source regarding matza are brought as difficulties to one or both of the opinions, but all are resolved.