Numbers 18:1-7 . THE CHARGE OF THE PRIESTS AND LEVITES.
19. it is a covenant of salt--that is, a perpetual ordinance. This figurative form of expression was evidently founded on the conservative property of salt, which keeps meat from corruption; and hence it became an emblem of inviolability and permanence. It is a common phrase among Oriental people, who consider the eating of salt a pledge of fidelity, binding them in a covenant of friendship. Hence the partaking of the altar meats, which were appropriated to the priests on condition of their services and of which salt formed a necessary accompaniment, was naturally called "a covenant of salt" ( Leviticus 2:13 ).
Numbers 18:21-32 . THE LEVITES' PORTION.
21, 22. I have given the children of Levi all the tenth in Israel for an inheritance, for their service which they serve--Neither the priests nor the Levites were to possess any allotments of land but to depend entirely upon Him who liberally provided for them out of His own portion; and this law was subservient to many important purposes--such as that, being exempted from the cares and labors of worldly business, they might be exclusively devoted to His service; that a bond of mutual love and attachment might be formed between the people and the Levites, who, as performing religious services for the people, derived their subsistence from them; and further, that being the more easily dispersed among the different tribes, they might be more useful in instructing and directing the people.
23. But the Levites shall do the service of the tabernacle of the congregation: they shall bear their iniquity--They were to be responsible for the right discharge of those duties that were assigned to them, and consequently to bear the penalty that was due to negligence or carelessness in the guardianship of the holy things.
26. the Levites . . . offer . . . a tenth of the tithe--Out of their own they were to pay tithes to the priests equally as the people gave to them. The best of their tithes was to be assigned to the priests, and afterwards they enjoyed the same liberty to make use of the remainder that other Israelites had of the produce of their threshing-floors and wine-presses.
32. ye shall bear no sin by reason of it, &c.--Neglect in having the best entailed sin in the use of such unhallowed food. And the holy things would be polluted by the reservation to themselves of what should be offered to God and the priests.