Responsa for Bava Batra 108:2
אמר רב יהודה אמר שמואל נכסי עובד כוכבים הרי הן כמדבר כל המחזיק בהן זכה בהן מאי טעמא עובד כוכבים מכי מטו זוזי לידיה אסתלק ליה ישראל לא קני עד דמטי שטרא לידיה הלכך הרי הן כמדבר וכל המחזיק בהן זכה בהן
<font>Rab Judah said in the name of Samuel: The property of a heathen<span class="x" onmousemove="('comment',' The reference, as appears from what follows, is to property sold by a heathen to an Israelite who has paid the money but not yet received the deed of sale. ');"><sup>3</sup></span></font> is on the same footing as desert land; whoever first occupies it acquires ownership. The reason is that as soon as the heathen receives the money he ceases to be the owner, whereas the Jew does not become the owner till he obtains the deed of sale.<span class="x" onmousemove="('comment',' The rule was that if a Jew bought land from a Jew, it remained in the ownership of the seller until the purchaser had received the title-deed, and either could retract until that time. But if a heathen sold land to a Jew, neither could retract so soon as the money had been paid, though in this case too the Jew did not become owner till he had received the title-deed. ');"><sup>4</sup></span>
Teshuvot Maharam
A. A and C cannot force B to transfer the house to them, for the following reasons: a) B denies having promised A and C not to buy the house; b) if B did make such a promise to A and C, and then broke it he might be called Rasha (wicked) or Abaryana (renegade), but we can not force him to transfer the house to A and C; therefore, no useful purpose will be served by imposing an oath on B regarding such promise; c) although locking a house is considered a valid act of possession, and one may gain title to the property of a Gentile by taking possession thereof (Bechorot 13a), this rule applies only when such an act is accompanied by proper intention by both parties. However, before the two parties agree on the terms of the sale no such intention is possible; therefore, A's locking of the Gentile's house was of no consequence; d) the fact that the Gentile owed money to A does not vest in him the priority rights of an abutter, for, only a creditor who has a mortgage on a house, lives therein, and has a lease thereon so that he cannot be made to move before the year is up has the right of an abutter. Moreover, since A's property borders on that of the Gentile, B may assert: "I have driven away a lion from your neighborhood", and such assertion annuls the priority rights A could have claimed as an abutter, as a creditor, or as a partner; e) B's statement to the arbitrators constituted neither an oath nor a vow, but a mere assurance. Even if we agree with A, who has construed that statement to mean an oath, B may not be forced to transfer his house to A merely because he disregarded his oath. Thus A is not entitled to indemnity. Indeed, B should be fined for his sinful act (breaking his oath), but we do not have the authority to impose penalties. However, you, my teacher, and your community, if you find that a disgraceful breach of conduct was committed, you may impose a proper fine upon B, the money to go to charity. Finally, half of B's wall, upon which the ends of A's beams are resting, belongs to A; for, the presence of such beams is ample proof that the wall was held in partnership by the two neighbors.