John Calvin Commentary Deuteronomy 18:1

"The priests the Levites, [even] all the tribe of Levi, shall have no portion nor inheritance with Israel: they shall eat the offerings of Jehovah made by fire, and his inheritance." — Deuteronomy 18:1 (ASV)

The priests, the Levites, and all the tribe of Levi. This chapter contains three principal points. First, God shows that there was no reason why the Israelites should be aggrieved by paying tithes to the Levites and by presenting the first-fruits and other oblations to the priests, since this tribe was deprived of their inheritance. Secondly, He prevents all quarrels and unlawful gains and petty thefts by assigning their just share to the priests and Levites. Thirdly, He defines how the oblations should be divided among them and what part of the victims the priests were to take.

Regarding the first point, since God was, so to speak, the lot of their inheritance, they justly claimed for themselves the right which He had transferred to them.

If it were disagreeable to the people that their revenue should be tithed, God intervened, so to speak, declaring that it was His property by His right as King, and appointed the Levites to be His stewards and collectors for receiving it.

Therefore, there was no ground for anyone to raise a dispute, unless he chose openly to rob God.

But this declaration often occurs, since it was of great importance that the people should be assured that God considered as received by Himself what He had assigned to the Levites. This assurance was intended not only to prevent any portion from being withheld from them, but also to ensure that everyone would willingly pay the lawful dues of God’s ministers; and furthermore, to prevent anyone from wickedly murmuring because the first-fruits and some portion of the sacrifices were designated for the priests' subsistence.

Another reason is also expressed why the honor assigned to the priests should be paid without grudging: namely, because God had appointed them to be the ministers of His service; and indeed, “the laborer is worthy of his hire.”