Question:
If someone gave me money to hold for him, and I borrowed it temporarily without his permission.... and then he showed up wanting it right away & I did not have it available to give him... can he ask for money damages? (damages for lost profit he could have made with the money I was holding for him) due to the fact that he lost out on a business deal that would have made him profit ?'
Answer:
Answer from Horav Y. Fleishman shlit"a
It is complex but you may have to give him the profits you earned-even in beis din. Look at the Ramo in siman 292 seif 7 and the Shach who brings a Maharshal who argues and there is a Pischei Teshuvo there. In denei shmayim there is a very good chance you are chayav-but for both these questions-it needs a hearing of both sides or look at these sources and see where your case fits
Sources: