Musannaf Ibn Abi Shayba 13:1527

Abu Bakr narrated to us, he said: Yazid bin Harun narrated to us, from Hisham, from al-Hasan, regarding a man who was given dirhams to buy something with them, so he spent them on his own need, then he returned them and bought with them what he was ordered to buy. He said: He is a guarantor until he delivers them to their owner.