Sayyiduna Abu Sa'id Khudri (may Allah be pleased with him) narrates: In the blessed time of the Prophet (peace and blessings of Allah be upon him), we used to sell two sa' of ordinary dates in exchange for one sa' of good dates. So the Prophet (peace and blessings of Allah be upon him) said: Two sa' of dates cannot be exchanged for one sa' of dates, and two sa' of wheat cannot be exchanged for one sa' of wheat, and two dirhams cannot be exchanged for one dirham.