The Geneva Bible Translation Notes, [1599], at sacred-texts.com
(a) That is, to serve in the most holy place, and to consecrate the holy things.
Now [concerning] Moses the man of God, his sons were named of the (b) tribe of Levi.
(b) They were but of the order of the Levites and not of the priests as Aaron's sons.
And the sons of Eliezer [were], Rehabiah the (c) chief. And Eliezer had none other sons; but the sons of Rehabiah were very many.
(c) The scripture calls him chief or first born even though he is alone and there is no one born after him, (Mat 1:25).
And Eleazar died, and had no sons, but daughters: and their (d) brethren the sons of Kish took them.
(d) Meaning their cousins.
These [were] the sons of Levi after the house of their fathers; [even] the chief of the fathers, as they were counted by number of names by their polls, that did the work for the service of the house of the LORD, from the age of (e) twenty years and upward.
(e) David chose the Levites twice, first at the age of thirty as in (Ch1 23:3) and again afterward at twenty as the office required: at the beginning they had no charge in the temple before they were twenty-five years old, and had none after fifty, (Num 4:3).
Because their office [was] to wait on the sons of Aaron for the service of the house of the LORD, in the courts, and in the chambers, and in the (f) purifying of all holy things, and the work of the service of the house of God;
(f) In washing and cleansing all the holy vessels.