Abu Sa'id and Abu Huraira told that God’s Messenger appointed a man over Khaibar and he brought him dates of a very fine quality. He asked him whether all the dates of Khaibar were like that, and he replied,“I swear by God that they are certainly not, Messenger of God. We take a sa‘ of this kind for two, and two for three." So he said, "Do not do so. Sell the lot for dirhams, then buy the very fine dates for dirhams." He said that it was the same when things were sold by weight. (Bukhari and Muslim.)