It is narrated from Sayyiduna Ibn Abbas (may Allah be pleased with them both) that when the Prophet (peace and blessings of Allah be upon him) arrived in Madinah, he found that the people there used to transact dates on credit for one, two, or three years. The Prophet (peace and blessings of Allah be upon him) said: "When you do a Salam sale in fruits, specify its measure, specify its weight, and fix its time."