Musannaf Ibn Abi Shayba 13:721

Abu Bakr narrated to us, he said: Ibn Abi Za’idah narrated to us, from Ibn Sirin, who said: A man was mentioned to Ibn Mas’ud who had lent a man a dirham and stipulated [the use of] the back of his horse. He said: Whatever he obtained from the back of his horse, it is usury (riba).