Is zakat obligatory upon the seller of crops or their buyer if the crops were sold before their grains ripened, and does the seller pay zakat on grains or on money if zakat became obligatory upon him and he had sold the crops for money?

Determining who is obligated to pay zakat on crops depends on the validity of the sale. Selling crops before their ripeness becomes apparent is prohibited and invalidates the sale if their cutting is not stipulated. So, if the questioner bought the crops before their ripeness became apparent, without the land, and did not stipulate their cutting, then the sale is void, and the crops belong to the seller, and the zakat is upon him, because the prohibition entails invalidity. The view of the majority of scholars is that it is impermissible to pay the value instead of the obligatory specific item.