משנה אויף בראשית 41:6

If one leased a field from his fellow and the locusts devoured the crop or it was blasted [by strong winds which caused the grain to be prematurely separated from the stalks], if it was a region-wide mishap he may reduce the amount of the rental agreement. If it was not a region-wide mishap, he may not reduce the amount of the rental agreement. Rabbi Judah says: “If he had leased it from him for a fixed amount of money, in neither case may he reduce the amount of the rental agreement.”