Numbers 3:14-20

"And Jehovah spake unto Moses in the wilderness of Sinai, saying, Number the children of Levi by their fathers' houses, by their families: every male from a month old and upward shalt thou number them. And Moses numbered them according to the word of Jehovah, as he was commanded. And these were the sons of Levi by their names: Gershon, and Kohath, and Merari. And these are the sons of Gershon by their families: Libni and Shimei. And the son of Kohath by their families: Areram, and Izhar, Hebron, and Uzziel. And the sons of Merari by their families: Mahli and Mushi. These are the families of the Levites according to their fathers' houses."

The effect of this very abbreviated genealogy is that of dividing the Levites into three divisions:

1. the Gershonites
2. the Kohathites, and
3. the Merarites

A marked difference in the method of numbering occurs here in that all males above the age of one month were included, whereas in the case of the military registration, only those above twenty years old were counted. Based upon this, Jewish tradition held that, "A child must live a month before being considered fully viable. Neither funeral nor mourning practices are observed if a child has not reached that age, and the child is considered as if stillborn."[12]