11 Now the Lord spoke to Moses in the Wilderness of Sinai, in the tabernacle of meeting, on the first day of the second month, in the second year after they had come out of the land of Egypt, saying: 2 "Take a census of all the congregation of the children of Israel, by their families, by their fathers' houses, according to the number of names, every male individually, 3 from twenty years old and above--all who are able to go to war in Israel. You and Aaron shall number them by their armies.
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.