Musannaf Ibn Abi Shayba 13:3239

Abu Bakr narrated to us, he said: Yazid narrated to us, from Hisham, from Ibn Sirin, that he used to see no harm in a man giving a deposit (*‘urbun*) to a boatman or someone else, and saying: "If you bring it by such-and-such a time, [then it is for me], and if not, then it is yours."