Narrated Ibn Abbas (may Allah be pleased with them) that the Messenger of Allah (peace and blessings of Allah be upon him) came to Madinah and at that time people used to do Salam (forward sale) in dates for one or two years. So the Prophet (peace and blessings of Allah be upon him) said: "Whoever does Salam in dates should do so according to a specified measure and a specified weight." In another narration from Ibn Abbas (may Allah be pleased with them), it is reported that the Messenger of Allah (peace and blessings of Allah be upon him) said: "He should do (Salam) in a specified measure for a specified period." (If cash is paid in advance for a certain period and the commodity (crop or any item) is received after that period, this is called "Salam".)

Narrated Ibn Abi Awfa (may Allah be pleased with him): "We used to practice Salam (advance payment sale) in wheat, barley, grapes, and dates during the time of the Messenger of Allah (peace and blessings of Allah be upon him), Abu Bakr As-Siddiq (may Allah be pleased with him), and Umar Farooq (may Allah be pleased with him)."

Narrated Sayyiduna Ibn Abi Awfa (may Allah be pleased with him):
We used to do salam (forward contract) with the farmers of Syria for wheat, barley, and olives for a specified measure and a specified period. It was asked whether you used to do this transaction with those who possessed the actual goods. Sayyiduna Ibn Abi Awfa (may Allah be pleased with him) replied: We did not use to ask them (whether they had the actual goods or not).