The buyer makes a purchase in Nissan and the witness signs. In Tishrei, the witness is proven to be a false witness.
The Gemara says we rule like Abaye, that we disqualify retroactively. Thus, the seller can claim he never sold and the buyer loses out.
The Artscroll note says that the Rabbis protected the buyer and declared the witness ineligible only from the time he was discredited and forward (like Rava).
Is the halachah today like the Rabbis, and not like Abaye despite the Gemara stating that the halachah followed him?
Barry Epstein, Dallas, USA
This is one of the six places where we rule like Abaye. The Gemara presents an opinion which maintains that Rava agrees with Abaye that the Torah invalidates the witness retroactively, but that Rava maintains that the Rabanan enacted that the witness is disqualified only from now on in order to protect the buyer. You are referring to Rava's reason; Abaye maintains that no such enactment was made. The Halachah follows Abaye.
D. Zupnik