Numbers 1:46
What an astonishing increase from seventy persons who went down into Egypt about 215 years before, where they had latterly endured the greatest hardships! Such was the effect of God's promise, which cannot fail.
Numbers 3:22
month old <02320 01121> [from a month old.]
The males of all the other tribes were numbered from twenty years old and upwards; but, had the Levites been numbered in this way, they would not have been nearly equal in number to the first-born 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 also be of all ages; and it appears to have been partly on this ground, that the Levites were numbered from a month old and upwards.
