Muhammad bin Abi al-Mujalid (may Allah have mercy on him) says: Abdullah bin Shaddad (may Allah have mercy on him) and Abu Burdah (may Allah have mercy on him) sent me to Ibn Abza and Ibn Abi Awfa (may Allah be pleased with them both). I asked the two of them about the salaf sale (advance payment), and they replied: "With the Messenger of Allah (peace and blessings be upon him) we used to receive a share of the spoils of war. Then the people of Syria would come to us, and we would make salaf contracts with them for wheat, barley and olive oil to a fixed term." It was said to them: "Did they have crops?" They replied: "We did not ask them about that."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب البيوع / 11092