Is it permissible to repurchase an item sold for cash with a different currency?
Chapter on Selling the Musarrah (Animal with milk retained in udder)
Al-Mughni
Book of Sales
Primary text
If an item is sold on credit using a commodity (non-monetary item) and then bought back with cash, it is permissible. Similarly, if the original sale was for cash, and the repurchase is made in a commodity, it is permissible. This is because the prohibition is linked to the suspicion of Riba (usury), and there is no Riba between currency (Athman) and commodities (Urood). If an item is sold for one currency (e.g., two hundred dirhams) and then repurchased for a different currency (e.g., ten dinars), it is permissible because they are two distinct monetary types between which a surplus is allowed, similar to buying back with a commodity or repurchasing at the same price.
Supporting text
Abu Hanifa holds that repurchasing with a different currency is impermissible by Istihsan (juridical preference), viewing both currencies as functionally equivalent in terms of being a price, and seeing this as a means to Riba, analogous to repurchasing with the original currency type.