Adam Clarke on Matthew 21:34

He sent his servants - Prophets, which, from time to time, he sent to the Jewish nation to call both priests and people back to the purity of his holy religion.

Receive the fruits of it - Alluding to the ancient custom of paying the rent of a farm in kind; that is, by a part of the produce of the farm. This custom anciently prevailed in most nations; and still prevails in the highlands of Scotland, and in some other places. The Boldon book, a survey made of the state of the bishopric of Durham in 1183, shows how much of the rents was paid in cows, sheep, pigs, fowls, eggs, etc., the remaining part being made up chiefly by manual labor.