What is the ruling on disposing of money sent by the maternal uncle to the grandfather via an agent in local currency, knowing that the uncle deems this transaction permissible to alleviate hardship and difficulty, and that sending the message takes the place of immediate possession, and that the fundamental principle in transactions is permissibility?

In currency exchange (sarf), immediate possession is required, whether actual or constructive. Receiving a check, a remittance slip, or an entry in the bank's ledgers serves as a substitute for actual possession. However, a message from the money holder to the other party is not considered possession. The basic principle in transactions is permissibility, unless prohibited by Sharia. Sharia has prohibited riba al-nasi'a (usury of delay) in currency exchange, and alleviating hardship does not justify engaging in forbidden acts.

If the uncle continues his prohibited method of transfer, he commits a sin by engaging in riba al-nasi'a, and the money is not lawful for the recipient because the exchange contract is invalid and thus does not confer ownership. Ibn al-Mundhir said: "All scholars whom I recall have unanimously agreed that if two parties to an exchange separate before taking possession, the exchange is void." Ibn Qudamah said: "Sarf (currency exchange) is the sale of currencies for one another. Possession in the same session is a condition for its validity, without dispute."

If the uncle does not change his mind, there is no sin upon the questioner for living with his grandfather. And even if the uncle is the one providing for them, the sin of the prohibited transaction falls upon the one who engaged in it, who is the owner of the money transferred in this invalid way. Money earned through prohibited means is forbidden only to the earner, and if it is transferred to another through a permissible means, it becomes lawful for them to benefit from it.