Gittin 58B

תניא כוותיה דשמואל, רבי שמעון בן אלעזר אומר: לקח מן האשה, וחזר ולקח מן האיש ⁠– מקחו קיים. מן האיש, וחזר ולקח מן האשה ⁠– מקחו בטל, עד שתכתוב לו אחריות.

It is taught in a baraita (Tosefta 5:2) in accordance with the opinion of Shmuel that R' Shimon ben Elazar says: If one first purchased a field belonging to a married woman from the wife, so that if her husband were to predecease or divorce her, the purchaser would then own it fully, and afterward he returned and purchased the same field from the husband, so that he will have the right to use it in the interim, his purchase stands. If he first acquired the field from the husband, and afterward he returned and purchased the same field from the wife, his purchase is void, unless the woman writes him a guarantee. This supports Shmuel’s opinion that only when the prior owner writes the buyer a guarantee is it assumed that he sold him the field wholeheartedly.

נימא תיהוי תיובתא דרב? אמר לך רב: מאי ״אחריות״⁠ – נמי שטר.

The Talmud asks: Let us say that this baraita is a conclusive refutation of the opinion of Rav, who said that a written bill of sale suffices and a guarantee is not required. The Talmud answers: Rav could have said to you: What is the guarantee mentioned here? It too is referring to a bill of sale, as it suffices that she sell him the field with a bill of sale, and it is not necessary for her to write him a guarantee in addition.

תנו רבנן: לקח מן הסיקריקון, ואכלה שלש שנים בפני בעלים, וחזר ומכרה לאחר ⁠– אין לבעלים על לוקח שני כלום.

A baraita states: If one purchased land from a Sicarius and consumed its produce for 3 years in the presence of the prior owner, and then the one who purchased it from the Sicarius returned and sold it to another person, the prior owner has no claim against the second buyer.