Sayyiduna Abu Sa'id Khudri (may Allah be pleased with him) narrates that during the time of the Messenger of Allah (peace and blessings be upon him), we were given inferior dates to eat, so we used to give two sa's (of inferior dates) and take one sa' (of good dates). When this matter reached the Messenger of Allah (peace and blessings be upon him), he said: "It is not permissible to give two sa's in exchange for one sa', nor is it permissible to give two dirhams in exchange for one dirham."