Numbers 1:18-20

21st Century King James Version

¹⁸ And they assembled all the congregation together on the first day of the second month; and they declared their pedigrees according to their families, by the house of their fathers, according to the number of the names, from twenty years old and upward by head count.

¹⁹ As the Lord commanded Moses, so he numbered them in the Wilderness of Sinai.

²⁰ And the children of Reuben, Israel’s eldest son, by their generations, according to their families, by the house of their fathers, according to the number of the names, by head count every male from twenty years old and upward, all who were able to go forth to war: