20 Now the sons of Reuben , Israel's firstborn , their genealogical registration by their families , by their fathers' households , according to the number of names , head by head , every male from twenty years old and upward , whoever was able to go out to war ,
Matthew Henry's Commentary on Numbers 1:20
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.