1)RETRACTING AN OFFER
(a)(R. Aba): Reuven charged Shimon 'you stole my slave', and Shimon denied it, and said 'he is with me because you sold (or gave) him to me', and said 'if you want to swear that he is yours, you may have him.
1.Once Reuven swears, Shimon cannot retract his offer.
(b)Question: We already learn this from a Mishnah!
1.(Mishnah - R. Meir): If Levi told Yehudah 'I allow you to use for judges (in our case) my father, or your father, or these three shepherds', Levi can retract;
2.Chachamim say, he cannot retract.
(c)Answer: R. Aba teaches that they argue in a case that Levi is the defendant (he agreed to pay if the invalid judges will obligate him. All agree that if Levi is the claimant, and agreed to exempt Shimon if the invalid judges will exempt Shimon, Levi cannot retract), and that the Halachah follows Chachamim. (Other Amora'im explain that they argue only when Levi is the claimant.)
(d)(R. Aba): The Halachah is, a lender can collect slaves from the borrower's heirs.
(e)(Rav Nachman): He cannot collect slaves.
(a)(R. Aba): The Halachah is, a third (generation, i.e. grandson) (of Reuven) can testify about a second (generation of Reuven's brother, i.e. Shimon's son).
(b)(Rava): A third can even testify about a first (Shimon).
(c)(Mar bar Rav Ashi): He can even testify about his own grandfather.
(d)The Halachah does not follow Mar bar Rav Ashi.
(e)(R. Aba): If Levi knew testimony about land, then he became blind, he cannot testify.
(f)(Shmuel): He may testify, e.g. if he knows signs delineating the borders of the land;
1.He cannot testify about a garment,
(g)(Rav Sheshes): He can even testify about a garment, e.g. if he knows the length and width;
1.He cannot testify about an ingot (chunk of metal).
(h)(Rav Papa): He can even testify about an ingot, e.g. if he knows its weight.
(i)Question (Beraisa): If Reuven knew testimony about Shimon, then he became Shimon's father-in-law, or deaf, blind, or insane, he cannot testify;
1.If he was a valid witness when he saw the testimony, then he became his father-in-law, deaf, blind, or insane, and later became valid again (Reuven's daughter died, so he is no longer related, or he regained his hearing, sight or sanity), he can testify;
2.The general rule is, if he was an invalid witness at the beginning (when he saw the testimony) or the end (when he wants to testify), he cannot testify. If he was a valid witness at the beginning and at the end, he can testify.
(j)This refutes Shmuel, Rav Sheshes and Rav Papa.
3)OTHER TEACHINGS OF R. ABA
(a)(R. Aba): If one says (we will explain what) about a child among children, he is believed;
(b)(R. Yochanan): He is not believed.
(c)Question: What does this mean?
(d)Answer #1 (Abaye): R. Aba says that if one says about one of his sons 'he will inherit all my property', he is believed. This is like R. Yochanan ben Brokah (130a);
1.R. Yochanan says that he is not believed. This is like Chachamim.
(e)Objection (Rava): If so, why do they say 'believed' and 'not believed'? They should say 'he inherits' or 'he does not inherit'!
(f)Answer #2 (Rava): R. Aba says that if one says about one of his children 'he is my firstborn', he is believed. This is like R. Yehudah (127b);
1.R. Yochanan says, he is not believed. This is like Chachamim.
(g)(R. Aba): If Reuven says 'my wife will receive a share of my property like one of my sons', this takes effect.
(h)(Rava): She receives a share of the property that he had when he said this. She receives a share of this (a half or third or quarter...) based on the number of sons he has when he dies.
(i)(R. Aba): If Shimon brought a loan document against Levi and says that he did not collect any part of it, and Levi says that he paid half, and witnesses testify that he paid it all, Levi swears that he paid half, and Shimon collects half from Levi's free (unsold) property;
1.He cannot collect from what Levi sold, for the buyer can say 'witnesses testified that it was paid!'
2.(If a loan document says 'Sela'im' (this implies at least two), the lender claims five, and the borrower (Yehudah) admits to three, R. Akiva exempts Yehudah from swearing, like a Meshiv Aveidah (one who returns a lost object, for he could have said two). R. Shimon ben Elazar obligates him to take the oath of Modeh b'Miktzas (partial admission).
3.Only there, R. Akiva considers him like a Meshiv Aveidah, for there are no witnesses. Here, Levi admitted to half due to fear of the witnesses (lest they support Shimon), therefore he must swear.
(j)Objection (Mar bar Rav Ashi): Just the contrary! Even R. Shimon ben Elazar obligates swearing Modeh b'Miktzas only there, for witnesses do not support him. Here, witnesses support Levi (he could have denied owing anything), so he is like a Meshiv Aveidah, and he does not swear.
(k)(Mar Zutra citing Rav Ashi): The Halachah follows R. Aba in all these teachings.
(l)Question (Ravina): Rav Nachman argues! (He says that we do not collect from slaves, and the Halachah follows Rav Nachman in monetary laws.)
(m)Answer (Rav Ashi): We learned that also R. Aba said that we do not collect from slaves.