Muwatta 1940

Malik says of a man who said to another: I will buy from you these fifteen sa's of Ajwa dates, or ten a'sa' of Sayhani dates, or fifteen sa's of carried wheat, or ten a'sa' of Syrian wheat, for a dinar, one of them being due to me. This is disliked and not permitted. He had made due for him ten a'sa' of Sayhani dates, and he leaves them and takes fifteen sa's of Ajwa, or fifteen sa's of carried wheat fall due on him, and he leaves them and takes ten a'sa' of Syrian wheat. This is also disliked and not permitted. It resembles what was forbidden as two sales in one sale, and is also what was forbidden, that one food of one kind be sold two for one. ¹

Belongs to the Muwatta, Book of Sales. Source: the Muwatta. Mentions Malik ibn Anas. Built on in the chapters on sale and riba.