[Ruling on Selling Fodder Before Harvest]

Answer—and Allah is the Granter of success: It is preferable that the seller pay the zakat from the price received if it reaches the niṣāb or more.
There is no zakat on the buyer unless he leaves it until harvest; if he leaves it until harvest, then zakat is due upon him, due to His saying, Exalted is He: “And give its due on the day of its harvest.” [al-Anʿām:141].
Source : Min Thimār al-ʿIlm wa al-Ḥikmah vol.1