It was narrated that Ibn "Abbas said:

The Messenger of Allah (ﷺ) forbade muhaqalah and muzabanah[1], and ‘Ikrimah regarded it as makrooh to sell wheat or barley harvested when it is green. [1]Muhaqalah means selling the field for a known measure of grain. Muzabanah means selling the palm tree for some wasqs of dried dates.