That are able to go forth to war It would seem from this that none of the aged and infirm were numbered, as being unable to go to war. Among several other nations as well as the Jews, particularly the Romans, all who were of age to bear arms were obliged, upon some occasions, to go forth to battle. And hence it is that we read of the kings of Israel bringing such numerous armies into the field as appear hardly credible to those who judge of their manners by ours.
Related Commentaries of Numbers 1:3
Numbers 1:3
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 armies.