11 And Jehovah spake unto Moses in the wilderness of Sinai, in the tent of meeting, on the first day of the second month, in the second year after they were come out of the land of Egypt, saying, 2 Take ye the sum of all the congregation of the children of Israel, by their families, by their fathers' houses, according to the number of the names, every male, by their polls; 3 from twenty years old and upward, all that are able to go forth to war in Israel, thou and Aaron shall number them by their hosts.
Matthew Henry's Commentary on Numbers 1:1-3
Commentary on Numbers 1:1-43
(Read Numbers 1:1-43)
The people were numbered to show God's faithfulness in thus increasing the seed of Jacob, that they might be the better trained for the wars and conquest of Canaan, and to ascertain their families in order to the division of the land. It is said of each tribe, that those were numbered who were able to go forth to war; they had wars before them, though now they met with no opposition. Let the believer be prepared to withstand the enemies of his soul, though all may appear to be peace.