Musannaf Ibn Abi Shayba 13:39

Muhammad ibn Maysarah narrated to us, from Ibn Jurayj, from ‘Amr ibn Shu‘ayb, from his father Shu‘ayb, that ‘Abdullah ibn ‘Amr used to have forward sales (salam) for food. He said to the one with whom he had the forward sale: "Do not take some of our wealth and some of our food, but rather take all of our capital or the food in full."