“And they assembled all the congregation together on the first day of the second month, and they declared their pedigrees after their families, by the house of their fathers, according to the number of the names, from twenty years old and upward, by their polls.”
King James Version (KJV)
1:19 He numbered them - For ought that appears in one day.
1:20 By their generations - That is, the persons begotten of Reuben's immediate children, who are here subdivided into families, and they into houses, and they into particular persons.