Musannaf Ibn Abi Shayba 13:1415

Abu Bakr narrated to us, he said: Yahya ibn Ya'la narrated to us, from Uthman ibn al-Aswad, from Mujahid, who said regarding the wealth of the orphan: If you trade with it and make a profit, then it belongs to him. If it is lost, you are liable. And if you place it [in safekeeping] and it perishes, then there is nothing upon you.