Bava Metzia 3 - Shabbat March 2, 22 Adar 1

The Gemara continues to compare the law in our Mishna to tannatic opinions in other cases of disputed money that seem to reach different halakhic conclusions. Distinctions are made between the various cases to prove that our Mishna could match the opinions of the tannaim in those sources as the details of our case are different and would therefore lead to a different ruling. Rabbi Chiya rules that if the defendant denies a claim but witnesses testify that the defendant owes half the contested amount, the defendant must pay half and take an oath on the other half to be exempt from payment. He derives this from kal v'chomer from modeh bemiktzat (one who admits to half a claim, where the law is that he/she takes an oath on the other half to be exempt).  The Gemara brings our mishna as proof for this law of Rabbi Chiya and then explains why there was a need for a kal v'chomer. As Rabbi Chiya did not explain the kal v'chomer from which he derived this law, the Gemara attempts to determine how it was derived. However, the first suggestion is that the lenient part of the kal v'chomer argument is a case of confession, but that is rejected as it is actually more stringent in one way than a case of witnesses. There are four attempts to explain why a confession is more stringent, but the first three are rejected. The final attempt to  find a stringency in confession over witnesses is that other witnesses cannot undo it, and that answer is accepted. The second suggestion, one witness, is rejected as the case where one witness can obligate the claimant to take an oath is referring to an oath on the part the witness testified about, whereas the two witnesses in our case are obligating an oath on the part that they did not testify about. Therefore, one cannot learn from one to the other.