If two people accidentally exchange sandals, is it permissible for one of them to use the sandal in his possession until he finds its owner, or must he buy another pair of sandals? And does the ruling differ if the mistake was made by the other party who gave a different sandal?

If the owner of the footwear made a mistake and initiated the exchange, and the other person knew or strongly believed that the one who took his footwear was the owner of the left-behind footwear, then there is no blame on him for taking and using it. Otherwise, the rulings of lost property apply to it.

If a person finds another's footwear in the place of his own, the original principle is that he should leave it and not take it; because it is possible that his footwear was taken by someone other than the owner of this footwear, in which case this person would have taken something that does not belong to him. If the two pairs of footwear are similar, and the owner of the footwear took another's footwear, thinking it was his own, then there is no blame in him taking it.

However, if two men entered the mosque and placed their footwear in the footwear collection area, then one of them left before the other and took his companion's footwear, and the second one left and did not find his footwear, but found the footwear of the one who took his, then there is no harm in him taking this footwear if he despairs of its owner's return.

And whoever lent his footwear to another, then was given a different pair of footwear in return, must return it to him. It is not permissible for him to benefit from it unless its owner willingly allows it, or he despairs of returning it to him.