Numbers 1:45

Overview - Numbers 1
1	God commands Moses to number the people.
5	The princes of the tribes.
17	The number of every tribe.
47	The Levites are exempted for the service of the Lord.

Numbers 1:45  (King James Version)
So were all those that were numbered of the children of Israel, by the house of their fathers, from twenty years old and upward, all that were able to go forth to war in Israel;