What is the ruling on selling the widely practiced "Nibal" in Sudan, where the crop is purchased cash from the farmer, then another person comes and writes a check for a higher amount, deferring payment for several months to take the crop directly?

It is permissible to sell fava beans after taking possession of them from the farmer. Possession is achieved by measuring or weighing them and setting them apart. However, selling them before taking possession is not permissible. There is a consensus (Ijma') prohibiting this, based on the Prophet's (peace be upon him) prohibition of selling food until the two measures (sa'an) are completed in it.