Musannaf Ibn Abi Shaybah

Ibrahim (may Allah have mercy on him) says that if a man owes someone some dirhams, and the creditor comes to him to demand repayment, and the debtor says, "Take instead of it wheat, dates, or anything other than gold," then there is no harm in that. When his dirhams are owed by another, he may take from him whatever he wishes in exchange.