Mukhtasar Muslim

It is narrated from Sayyiduna Abu Hurairah and Sayyiduna Abu Sa'id Khudri (may Allah be pleased with them) that the Messenger of Allah (peace and blessings of Allah be upon him) appointed a man from Banu Adi as the administrator of Khaybar. He brought Janib (a superior type of) dates. The Messenger of Allah (peace and blessings of Allah be upon him) asked him, "Are all the dates of Khaybar like this?" He replied, "No, by Allah, O Messenger of Allah! We buy one sa' of this date for two sa' of mixed dates." The Messenger of Allah (peace and blessings of Allah be upon him) said, "Do not do so. Rather, take them equal for equal, or sell one kind and buy the other with its price. And similarly, if you sell by weight, then sell equal for equal."