John Calvin Commentary Numbers 5:9

"And every heave-offering of all the holy things of the children of Israel, which they present unto the priest, shall be his." — Numbers 5:9 (ASV)

And every offering. Until now, I have brought together the passages in which Moses discusses the office of the priests and have briefly explained them. I will now begin to discuss their rights, that is, the honor with which God invested them, so that they would be ready and cheerful in their obedience.

Here, however, Moses briefly addresses what he explains more fully in other passages, as we will soon see: namely, He assigns to the priests all the holy offerings, the various kinds of which He later lists. There were three principal reasons for this law:

1. So that what had already been dedicated to God would not be profaned by its indiscriminate use; for, so that the sacrifices might retain their proper dignity, it was necessary to distinguish the sacred from ordinary foods.
2. A vainglorious excess regarding the ceremonies was restrained. For if, after the victims were killed, all the flesh had been returned to the owners, a desire for ostentation²⁰⁷ would have developed among foolish men. The rich would have competed to gain applause, and after feasting magnificently, they would have offered the rest for sale. In this way, they would have abused their false pretense of worshipping God to acquire favor for themselves.
3. The third reason is what Paul mentions, namely, that it is just that the ministers of the altar should live by the altar (1 Corinthians 9:13). For although it is an unworthy thing for the servants of God to be attracted by their payment, God was nevertheless unwilling for the priests, who had freely given their labor to the worship of the sanctuary, to suffer from hunger, so that their eagerness would not be suppressed.

For if they wished to carry out their office properly, it was necessary for them to attend entirely to spiritual things and give up the care of their domestic affairs.

If anyone should object that these were incentives to greed, and that an excellent and profitable calling was offered to the priests, the reply is easy: whatever came to their share, since it was restricted to their own consumption, could not have been excessive in quantity. For they were not allowed to sell any of it, nor even to give it away to others, as we have already seen and as will be repeated later.

Thus, then, the foul dishonesty of those who taunt Moses as if he had enriched the priests with the spoils of the people is thoroughly refuted. For if there were any whose interests he would have wished to consider, surely his own sons would have been preferred above all; yet there is no reference to them here. Indeed, whatever he grants to the priests, he takes away from his own sons and their descendants, as if he purposely deprived them of advantages that were not otherwise unlawful.

In short, only the dignity of holy things was considered, without any attempt being made to enrich the priests.

²⁰⁷ “C’estoit pour inciter les gens a une fole convoitise de se monstrer, et faire leurs parades:” it would have incited men to a foolish ambition for ostentation and parade. — :” it would have incited men to a foolish ambition for ostentation and parade. — Fr..