It was narrated that 'Abdullah bin "Umar said: "The Messenger of Allah P.B.U.H forbade the Muzabanah. The Muzabanah means when a man sells the dates of his grove when they are still on the tree, for a measure of dry datespl or, if it is grapes, he sells them when they are still on the vine, for a measure of raisins; or if it is a crop, he sells it for food, estimating the amount (of the crop in the field). He forbade all of these things." (Sahih)