Musannaf Ibn Abi Shayba 13:465

Abu Bakr narrated to us, he said: Waki’ narrated to us, from Yazid bin Ibrahim, from al-Walid bin Abdullah bin Abi Mughith, from Mujahid, from Ibn Umar, regarding a man who bought a camel and wanted to return it and return a dirham along with it. He said: "There is no harm in it."