Gemara

2a (Mishnah): Reuven and Shimon are holding a garment. Reuven says 'I found it', and so does Shimon; Reuven says 'it is mine', and so does Shimon. Each swears that he does not own less than half, and they divide it.

If Reuven says 'it is all mine' and Shimon says 'it is half mine', Reuven swears that he does not own less than three quarters, and Shimon swears that he does not own less than one quarter. Each gets like he swore.

5b (Mishnah): Reuven swears that he does not own less than half...

Question: He should swear about what he owns, not about what he does not own!

Answer (Rav Huna): He swears that he owns part of it, and that he does not own less than half.

He does not swear that he owns all of it (like he claimed), for then it would seem improper that Beis Din gives to him only half. He does not swear that he owns half, for that would seem like a retraction of his claim that it is all his.

Question: The text of the oath of the Mishnah is also like a retraction!

Answer: The actual text is 'it is all mine. Since you do not believe me about this, I swear that I own part, and I do not own less than half.'

Question: Since each is holding half, why do they swear?

Answer (R. Yochanan): The oath of our Mishnah is a Rabbinical enactment, to deter people from grabbing others' property and claiming it.

6a (Beraisa): The case is, both are holding it. If one holds it alone, ha'Motzi me'Chavero Alav ha'Re'ayah (the other must bring a proof to take it).

Question: If only one holds it, obviously, it is his!

Answer: Reuven was holding the garment itself, and Shimon was holding onto the fringes. Even Sumchus, who holds that when in doubt, we divide the money without an oath, admits that holding onto the fringes is insignificant.

7a (Rav Tachlifa bar Ma'arava - Beraisa): If two are holding a garment, each gets up to where he is holding, and they divide the rest evenly.

R. Avahu gestured to him that they must swear.

Question: The Mishnah says that they divide (equally). It does not say that each gets up to where he is holding. What is the case?

Answer (Rav Papa): Each is holding it by the fringes.

Inference (Rav Mesharshiya): If one grabs three by three of a garment (given for Kinyan Chalipin), this fulfills "he gave to his fellowman" (he acquires), for it is as if the garment is cut (and he owns what is in his hand).

Rishonim

The Rif (3a) brings the Gemara on 7a.

Rambam (Hilchos To'en 9:7): If two were holding one Kli, and each says 'it is mine', each swears while holding a (Kodesh) Chefetz (e.g. Sefer Torah or Tefilin) that he does not own less than half, and they divide it. The oath is a enactment, lest one grab another's garment and receive (half) without swearing.

Rambam (9): If two are holding a garment, and each says 'it is all mine', each gets up to where he is holding, and they divide the rest evenly after swearing. Each can force the other to swear, through Gilgul, that he deserved all that he received.

Magid Mishneh: The Rambam explains that each receives what is under his hand without an oath. R. Avahu teaches that they swear about what is in the middle. Gilgul always applies. Rav Hai Gaon and Bahag agree. The Ra'avad explains that they must swear even to receive what they are holding. The Ramban and Rashba agree.

Rosh (13): When they are holding in the middle of the garment, each gets up to where he is holding, and they divide the rest evenly. Each must swear even about the part under his hand, lest people grab others' property and claim it. If not, R. Avahu taught no Chidush (that each swears about the remainder in the middle that they divide). Our Mishnah teaches this! The Mishnah discusses when he is holding less than three by three at the end. It is not important enough to receive before (swearing and) dividing the rest.

Poskim

Shulchan Aruch (CM 138:1): If two were holding one Kli, and each says 'it is mine', each swears (while holding a Chefetz) that he owns (at least) part, and he does not own less than half, and they divide it.

Question (Nimukei Yosef 2b DH Zeh, citing the Ran): Why did the Rif and Rambam omit the text that the Gemara concluded?

Answer #1 (Beis Yosef DH Shnayim): The Rambam and Tur hold that the Gemara explains the meaning of the oath, but the text is like the Mishnah said.

Drishah (1): Rashi explained that the Gemara asked that the text of the oath allows Rama'os (swindling). I say that the Rif, Rambam and Tur hold that it asked only that it is more reasonable to swear about what one owns. Alternatively, Rashi agrees that the Gemara did not fix the text of the oath. It merely teaches that they swear in a way that does not contradict their claims and leaves no room for Rama'os. The Rambam and Tur already explained that one swears according to the Da'as (understanding) of Hash-m and Beis Din. The Rif requires him to say before swearing that he owns the entire item, so there is no concern for Rama'os, for we make him swear according to Hash-m's Da'as.

Bach (1): Hagahos Alfasi, citing R. Yeshayah, says that even though one swears according to the Da'as of Beis Din, a judge should be stringent to make the oath explicit to exclude any possible Rama'os. The Nimukei Yosef (1a DH she'Ein) holds that we use the text of the Gemara.

Shulchan Aruch (3): This is when they hold the garment by the end; neither holds three by three (fingers).

Shach (4): Since less than three by three is not important, it is improper to say that he receives it before dividing. However, if he wants to, he may. The Rosh connotes like this.

R. Akiva Eiger: It seems that the Prishah (3, who says that seizure does not apply to less than three by three) and Ir Shushan disagree.

Shulchan Aruch (ibid): If each holds part in his hand, and says 'it is all mine', each gets up to where he is holding, and they divide the rest evenly after swearing, like we said. Each can force the other to swear, through Gilgul, that he deserved all that he received.

Beis Yosef (DH Aval): The Tur holds like the Ra'avad, that each must swear to get even what he is holding.

SMA (11): Why did the Shulchan Aruch and Rema not bring the opposing opinion? It is the majority (four, including the Tur), and they are Basra (lived later than Rav Hai Gaon, Bahag and the Rambam)!

Toras Chayim (Bava Metzia 7a DH Hachi): The text says 'they divide the rest with an oath.' Tosfos deleted these words. If so, why did the Gemara ask in what case they divide and each swears about half? They do so whenever they hold equal amounts! The Beraisa teaches about when one holds more than the other. Even though the oath is to deter people from grabbing others' property (and it should apply to what each holds), what each holds is as if it was cut off, and each wants to take it from the other. The oath of our Mishnah was not enacted for this. The Gemara said that if one holds all of it, ha'Motzi mi'Chavero Alav ha'Re'ayah. Also the Nimukei Yosef connotes like this. The Gemara asked, for they cannot hold equal amounts, for if so the Mishnah should have taught that each receives what he holds without an oath. Rather, the Mishnah connotes that no one gets anything without swearing (i.e. when they hold the fringes). The Rambam and Shulchan Aruch say that each gets what is in his hand without swearing.

Rebuttal (Shach 5): Also the Bach rules like this. The primary Perush of the Gemara is like most Poskim say, that each must swear to get what he holds. Tosfos says that this is to deter people from grabbing others' property and claiming it. The Rosh and Rashba say that surely R. Avahu did not teach only that each swears about the remainder, for the Mishnah teaches this! The Gemara asked why the Mishnah did not teach that each (swears and) receives what he holds, and they divide the rest. This would include the case when they hold the fringres. We cannot say that they hold equal amounts, for then the law would be different in the Seifa (when one claims only a quarter). If the other holds three quarters, he would get it even if he claiimed only three quarters! Rav Hai Gaon wrote that each must swear to get what he holds. Later, he wrote 'and they divide the rest through an oath.' I.e., the entire division depends on swearing. Bahag does not connote like the Rambam. He just cites the Gemara!

Gra (12): The Rambam learns from 6a and Rav Mesharshiya (7a), who derived that what is under one's hand, it is as if he alone holds it.