If a someone makes a transaction but he had something else in mind (דברים שבלב) then we would not take that into consideration when deciding whether the sale was valid. What if the other person (the new מוחזק) believes the דברים שבלב of the first person. Is there any source that says he should return the item because he believes the דברים שבלב of the other person?
Answer:
No, there is no need or reason to take into account the seller’s (or buyer’s) thoughts. The halachah is that ‘devarim shebalev’ are not devarim, and for matters of a sale they are entirely inconsequential.
Although later authorities discuss at length why this is so, the simple explanation is that in a sale transaction, both parties know that the only thing that matters is what is being said, because of the reliance of the other party on what the other declares. If thoughts would be taken into consideration there would be no way to complete a transaction, so that both parties rely on speech alone, and thus ‘devarim shebalev’ are irrelevant.
For the same reason, the Gra writes that when it comes to unilateral transactions we do take a person’s thoughts into account, because the issue of reliance doesn’t apply (see Kuntresei Shiurim, Kiddushin 21:9).
Best wishes.
