Muwatta 1942

Malik says: among sale of uncertainty and risk is when a man takes a thing whose animal has strayed, or whose slave has run away, and its price is fifty dinars, and another man says: I will take it from you for twenty dinars. If the buyer finds it, the seller owes thirty dinars; if he does not find it, the seller owes the buyer twenty. Malik said: there is another defect in this: if the strayed thing is found, one does not know whether it has increased or decreased in value, or what defects have befallen it. This is the greatest risk. ¹

Belongs to the Muwatta, Book of Sales. Source: the Muwatta. Mentions Malik ibn Anas. Built on in the chapters on uncertainty (gharar).