There is a rosh kollel who came over to me in beis medrash, put $100 into my hand, and told me to get a haircut (because he felt that I have long hair). I subsequently cut my own hair, as I do not trust the barbers to be careful with my peyos and beard. (Whether I am right or wrong to mistrust them is a different question). Am I obligated to return the money to the rosh kollel, or may I do with it as I see fit?
I do not feel comfortable asking him this question myself (if I should return the money to him), as he is a tzaddik and a yirei shomayim and money means nothing to him (and, of course, he is not going demand the money back from me, a bachur, due to his exceptional derech eretz); however, I want to do the right thing halachically, and at the same time I could use the money for other things. So the question is whether or not I should return the money to this tzaddik?
A haircut doesn’t cost $100, so obviousely he meant to give you the money for your own use.