Numbers 1:16-18

¹⁶These were the called ones of the congregation, princes of the tribes of their fathers, chiefs of the thousands of Israel were they.

¹⁷And Mosheh and Aharon took these men who were expressed by their names;

¹⁸And they assembled all the congregation on the first of the second month, and they declared their pedigrees according to the house of their fathers, with the number of their names from twenty years old and upwards, by their polling.