Numbers 1:19-21

Young's Literal Translation

¹⁹ as Jehovah hath commanded Moses; and he numbereth them in the wilderness of Sinai.

²⁰ And the sons of Reuben, Israel's first-born -- their births, by their families, by the house of their fathers, in the number of names, by their polls, every male from a son of twenty years and upward, every one going out to the host --

²¹ their numbered ones, for the tribe of Reuben, are six and forty thousand and five hundred.