R. ABA'S LAW OF THE INGOT
One witness testified in front of R. Ami that Reuven grabbed an ingot from Shimon. Reuven said 'yes, I grabbed it. It is mine!'
Question (R. Ami): What is the law? We cannot obligate Reuven based on one witness, nor can we totally exempt him!
Version #1 (Rashbam): We cannot require him to swear (to contradict the witness, and say that he did not take it), for he admits that he took it!
In this sense he is like a thief, who cannot swear. (However, a thief cannot swear because he is not believed.)
Version #2 (Rashba): We cannot require him to swear that he took his own ingot. Shimon was Muchzak in what he was holding. It is as if Reuven admits that he stole it!
Answer (R. Aba): He is obligated to swear, but he cannot, therefore he must pay.
ONE WITNESS FOR CHAZAKAH
Rejection (of Rabanan, Sof 33b - Abaye): Our case (one witness said that David ate the years of Chazakah) is unlike that of R. Aba!
In R. Aba's case, the witness comes to obligate Reuven. If a second witnesses were with him, all the more so Reuven would have to return it;
Here, the witness comes to support David. If a second witness were with him, David would keep the land and Peros! (Therefore, David does not pay for the Peros.)
(Abaye): Rather, if one witness testified that David ate the fruit for two years, we would learn from R. Aba's law. (Since David cannot swear that he did not eat, he would pay for the Peros for those years.)
DOES BEIS DIN SEIZE CONTESTED PROPERTY?
Question: Reuven and Shimon each claimed to own the same ship. Reuven came to Beis Din and said 'seize the ship until I bring witnesses.' Do we seize it?
Answer #1 (Rav Huna): We seize it.
Answer #2 (Rav Yehudah): We do not seize it.
Question: Reuven did not find witnesses. He asked Beis Din to release the ship, and Kol d'Alim Gavar (whoever overpowers the other (with proofs or physically) gets it). Do we release it?
Answer #1 (Rav Yehudah): We do not release it.
Answer #1 (Rav Papa): We release it.
The Halachah is, we do not seize it. If we seized it, we do not release it.