Muwatta 1962

Malik says: the practice among us about a man who buys goods from another, and they differ over the price: the seller says: I sold it to you for ten dinars, and the buyer says: I bought it from you for five dinars. It is said to the seller: if you wish, give it to the buyer at what he says, and if you wish, swear by God that you sold your goods only for what you said. If he swears, it is said to the buyer: either take the goods at the seller's price, or swear by God that you bought it only for what you said. If he swears, he is discharged from it, because each of them is a claimant against the other. ¹

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