It is narrated from Hazrat Abu Saeed Khudri (may Allah be pleased with him) that once Hazrat Bilal (may Allah be pleased with him) brought some dates to the service of the Prophet (peace and blessings be upon him). The Prophet (peace and blessings be upon him) found something unusual about the matter, so he asked him, "Where did you get these from?" He replied, "I exchanged two sa’ of inferior dates for one sa’ of these good dates." The Prophet (peace and blessings be upon him) said, "Oh! This is pure usury, do not go near it. Rather, first sell your own dates, then with that price buy whatever you wish."