Musnad Ahmad 319:1

Waki’ narrated to us, Isma’il ibn Ibrahim ibn ‘Abdullah ibn Abi Rabi’ah al-Makhzumi narrated to us, from his father, from his grandfather, that the Prophet, peace and blessings of Allah be upon him, borrowed thirty or forty thousand from him when he went out to the battle of Hunayn. When he returned, he repaid it to him, then said: "May Allah bless you in your family and your wealth. Indeed, the reward for a loan is repayment and praise."