Musnad Ahmad 775:2

Hashim narrated to us, Ash-Shaybani informed us, from Muhammad ibn Abi al-Mujalid, the freed slave of Banu Hashim, who said: Ibn Shaddad and Abu Burdah sent me, and they said: "Go to Ibn Abi Awfa and say to him: 'Abdullah ibn Shaddad and Abu Burdah send you greetings, and they say: Did you use to engage in *salam* (forward sales) during the time of the Messenger of Allah, may Allah bless him and grant him peace, for wheat, barley, and oil?'" He said: "Yes, we used to obtain spoils during the time of the Messenger of Allah, may Allah bless him and grant him peace, and we would engage in *salam* with them for wheat, barley, dates, and oil." I said: "Was it with those who had crops or those who did not have crops?" He said: "We did not use to ask them about that." He said: And they said to me: "Go to Abd al-Rahman ibn Abza and ask him." He said: So I went and asked him, and he said the same as what Ibn Abi Awfa said. And likewise, Abu Mu'awiyah narrated it to us, from Za'idah, from Ash-Shaybani, and he said: "And oil."