מדרש על בבא מציעא 55:6

"until your brother inquires concerning it": Would it enter your mind to give it to him without his giving identifying signs? Why, then, is it written "until your brother inquires concerning it"? (The meaning must be, then,) "until you make inquiry concerning your brother" (to ascertain) whether or not he is a deceiver, (this being a possible construction of the words in the Hebrew.)