Sahih Muslim Book 10, Hadith Number 3898.

Chapter : Prohibition of taking oath in business transactions.

Abu Huraira (Allah be pleased with him) reported: Allah’s Messenger (may peace be upon him) owed (something) to a person. He behaved in an uncivil manner with him. This vexed the Companions of the Holy Prophet (may peace be upon him), whereupon Allah’s Apostle (may peace be upon him) said: He who has a right is entitled to speak, and said to them (his Companions): Buy a camel for him and give that to him. They said: We do not find a camel (of that age) but one with better age than that. He said: Buy that and give that to him, for best of you or best amongst you are those who are best in paying off debt.