A month old and upward - The males of all the other tribes were numbered, from twenty years and upward; had the Levites been numbered in this way, they would not have been nearly equal in number to the firstborn of the twelve tribes. Add to this, that as there must have been first-born of all ages in the other tribes, it was necessary that the Levites, who were to be their substitutes, should be also of all ages; and it appears to have been on this ground, at least partly, that the Levites were numbered from four weeks old and upward.

Number the children of Levi,.... Who were left out of the general muster of the children of Israel, but now were to be numbered alone, and in a different manner, and for, a different purpose, the Lord having a special regard auto, them, and special service for them:

after the house of their fathers, by their families; into which the tribe was divided; house seems to be put for "houses", which were principal ones; and these were divided into families, which branched from them, and according to these, denominated from their fathers, and not their, mothers, were they to be numbered; for as the Jewish writers often say, a mother's family is no family; wherefore, if a Levite woman married into any other tribe, as she might, her, descendants were not taken into this accounts only such whose fathers were Levites, see Numbers 1:2,

every male from a month old and upwards shalt thou number them; the reason of this was, because the firstborn, for whom they were to be exchanged, were at a month old claimed by the Lord as his, and to be redeemed; and as this numbering was on, another account than, that of the children of Israel, who were numbered from twenty years of age and upwards, that they might on occasion be called out to war, from which the Levites were exempted, and the numbering of them was for the service of the sanctuary; so from their youth they were to be brought up and trained for this, that they might be fit for it, and enter upon it at a proper age.

Number the children of Levi after the house of their fathers, by their families: every male from a month old and upward shalt thou number them.

3:15 From a month old - Because at that time the first - born, in whose stead the Levites came, were offered to God. And from that time the Levites were consecrated to God, and were, as soon as capable, instructed in their work. Elsewhere they are numbered from twenty - five years old, when they were entered as novices into part of their work, Num 8:24, and from thirty years old, when they were admitted to their whole office.

3:14-39 The Levites were in three classes, according to the sons of Levi; Gershon, Kohath, and Merari; and these were subdivided into families. The posterity of Moses were not at all honoured or privileged, but stood upon the level with other Levites; thus it was plain, that Moses did not seek the advancement of his own family, or to secure any honours to it. The tribe of Levi was by much the least of all the tribes. God's chosen are but a little flock in comparison with the world.