Sahih Muslim Book 10, Hadith Number 3878.

Chapter : He who took something as loan and made its payment back, over and above that (19 approved) and best among you is one who is best in making payment.

Ibn ‘Abbas; (Allah be pleased with them) reported on the authority of Usama b. Zaid Allah’s Messenger (may peace be upon him) as having said this: There is no element of interest when the money or commodity is exchanged hand to hand.