Bava Batra 114 - Time to Reconsider an Agreement
When two parties want to formalize a verbal agreement, they often perform an " exchange acquisition " where one party hands the other a small article such as a kerchief and the second party takes possession of it.
Whenever this happens, parties are entitled to retract for a certain period of time. For how long? Rabbah said, "As long as they are seated at the same location." Rav Yosef said, "As long as there are talking about the same subject."
However, both Rabbah and Rav Yosef have a problem with the rule learned previously about a court executing the last will . If a sick person can retract, none of their decisions are valid! Rav Yosef answers that this rule is only applicable while they are still talking about the subject of inheritance.
Art: Antonio Paoletti - Fair Exchange