Six years ago I gave my brother-in-law 1000 EGP to buy a gold chain, which he never did. He now wants to return 1000 EGP to me. Please note that he used this sum to conduct business and in fact gained a profit from it. Is this legally permissible?
If the case is as mentioned in the question, it is obligatory upon the inquirer's brother-in-law to do either of the following:
Give her the amount of gold that could have been purchased by 1000 EGP six years ago.
Give her the equivalent sum of the gold according to the current price.
The above answers the question and Allah the Almighty knows best.