Musannaf Ibn Abi Shayba 13:2047

Abu Bakr narrated to us, he said: Ibn Abi Za’idah narrated to us, from Abu Hani’, from ‘Amir, who said: I read the document of the people of Najran and I found in it: "If you consume usury, then there is no peace treaty between us and you." And the Prophet, peace and blessings of Allah be upon him, would not make a peace treaty with one who consumes usury.