Musannaf Ibn Abi Shayba 13:1445

Abu Bakr narrated to us, he said: Ibn Abi ‘Adi narrated to us, from Ash’ath, from al-Hasan, regarding a man who enters into a forward sale (salam) and says: "If it is wheat, then it is for such-and-such, and if it is barley, then it is for such-and-such." He said: He disliked it.