Sahih Muslim
The Book of Transactions (Kitab Al-Buyu)
Book Number: 010 / Hadith Number: 3899
Abu Huraira (Allah be pleased with him) reported: Allah's Messenger (may peace be upon him) took a camel on loan, and then returned him (the lender) the camel of a more mature age and said: Good among you are those who are good in clearing off the debt.