Bava Batra 170 - One Who Makes Superfluous Claims in Court Must Stand by Them

If the occupant of a property comes to litigate with a previous owner concerning ownership of the property and asserts that he can prove that the property is his with both a deed and a chazakah (three years occupancy) - then Rebbi says that he is judged based on the deed. Rabbi Shimon ben Gamliel says that he is judged based on chazakah. What is the reason behind their argument?

Rav Dimi says that the deed was in the name of a third party, and the argument is whether the deed transfer also transfers property. Abaye says that invalid witnesses signed, and the argument is about which witnesses accomplish the transfer - those who sign or those who see it. R' Avina (Ravina) says that they argue whether one who made a superfluous claim is now required to corroborate it, with Rebbi saying "no" and Rabbi Shimon saying "yes."

Art: Notary Kohne and His Clerk by Wybrand Hendriks