Muwatta 1786

Malik says of a man who buys a slave or a slave-girl for a hundred dinars on credit, and then the seller regrets it and asks the buyer to cancel the sale for ten dinars paid in cash or on credit, and to erase the hundred dinars he is owed: Malik said there is no harm in that. If the buyer regrets it and asks the seller to cancel the sale of the slave-girl or slave, and adds ten dinars in cash or on a term later than the original term, that is not proper, because the seller has, as it were, sold him a hundred dinars due in a year, before it falls due, together with a slave-girl and ten dinars in cash or on a later term; and this involves a sale of gold for gold on credit. ¹

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