It is narrated from Sayyiduna Ibn Umar (may Allah be pleased with them both) that during the blessed era of the Prophet (peace and blessings be upon him), two men made a sale of fruit before it had come forth, but that year the fruit did not come at all. The Prophet (peace and blessings be upon him) said: "Why are you withholding his money?" After that, the Prophet (peace and blessings be upon him) forbade the sale of Salam until the fruit ripened.
Hadith Referenceمسند احمد / مسند المكثرين من الصحابة / 5236