I agreed orally to sell my house to Reuven and agreed to finalize the deal the next day. In the interim Shimon made an offer on the house that I accepted. Each one is demanding I honor my commitment to him. I shouldn’t have agreed to sell it to each of them, and I regret what I did.
Q: Am I obligated to sell the house to either one of them? Does one of them have priority?
A: There are different stages in making a kinyan — proprietary act. The transfer of property, whether real estate or movable objects, is effected only by means of a kinyan (C.M. 189:1, 241:1). Once a kinyan is performed the deal is completed and neither party may retract.
Partial kinyanim do not effect (validate) a transfer of property but Chazal recognize their effectiveness to the degree that one who reneges following a partial kinyan is subject to a curse — Mi shepara... — in beis din (C.M. 204:1, 4). For example, although Biblically, giving money to a merchant completes a kinyan of movable objects, nevertheless Chazal enacted that money without a physical transfer of the objects will not complete a kinyan. It does, however, subject either party to the curse if he reneges (C.M. 198:1,5).
In places where real estate transactions require documentation, the kinyan is not complete until the sale is documented (C.M. 190:7). However, many authorities maintain that an undocumented sale of real estate is a partial kinyan and one who reneges is subject to the curse (Pischei Teshuvah 204:2).
An oral commitment is not even a partial kinyan, and one who reneges is not subject to Mi shepara: nevertheless, he is considered mechusar amanah — lacking trustworthiness (C.M. 204:7) and he may be called a rasha — wicked person (Beis Yosef, Y.D. 264).
What is the halachah when one gave his word to two people but will only be able to honor one of those commitments? Does one of them take precedence? Perhaps a commitment to sell to a second person constitutes a retraction of his agreement to the first buyer and he now remains obligated to honor his commitment to the second buyer. On the other hand, perhaps a commitment to the second buyer does not constitute a retraction to the first buyer since the first buyer can have taarumos — complaints — and expect monetary reimbursement to satisfy his taarumos (Kesef Hakodashim 204:7). The Beis Yosef (Y.D. 264), however, subscribes to the view that when someone committed to two people to be the mohel for his child, he must honor his commitment to the first person (Minchas Pitim 204:11).
In your case, however, it would seem that you are not obligated to honor your commitment to either buyer. The fundamental principle of mechusar amanah is that there exists reliable intent — semichas daas — between the two parties to complete the transaction. For that reason a commitment to give a small gift constitutes a binding commitment, and if the benefactor retracts he is mechusar amanah. A pledge to give a large gift does not give the recipient semichus daas that he will receive that gift, and thus if the benefactor retracts his pledge, he is not considered mechusar amanah (C.M. 204:8; cf. Pri Yitzchak 1:51).
Nowadays, people do not have semichus daas for real estate transactions until a contract is signed, since numerous issues could occur that might cause the agreement to collapse. Therefore, a promise to sell your house to Reuven and Shimon did not generate semichus daas and thus you may sell to either one or neither one.