Muhammad, or Abdullah, bin Abi al-Mujalid (may Allah have mercy on him) said: Abdullah bin Shaddad and Abu Burdah differed about the advance sale (salaf), so they sent me to Ibn Abi Awfa (may Allah be pleased with him). I asked him, and he replied: We used to make advance sales in the time of the Messenger of Allah (peace and blessings be upon him), Abu Bakr and Umar (may Allah be pleased with them both) in wheat, barley, dates and raisins. Ibn Kathir added: we used to make this sale with people who did not have these things. Then the two narrations continue alike: I then asked Ibn Abza (may Allah be pleased with him) about the same matter, and he too gave the same answer.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب البيوع / 11091