Numbers 1:50

And he gave unto Moses, when he had made an end of communing with him upon mount Sinai, two tables of testimony, tables of stone, written with the finger of God.

Then Moses stood in the gate of the camp, and said, Who is on the LORD's side? let him come unto me. And all the sons of Levi gathered themselves together unto him. And he said unto them, Thus saith the LORD God of Israel, Put every man his sword by his side, and go in and out from gate to gate throughout the camp, and slay every man his brother, and every man his companion, and every man his neighbor. And the children of Levi did according to the word of Moses: and there fell of the people that day about three thousand men. For Moses had said, Consecrate yourselves today to the LORD, even every man upon his son, and upon his brother; that he may bestow upon you a blessing this day.

This is the sum of the tabernacle, even of the tabernacle of testimony, as it was counted, according to the commandment of Moses, for the service of the Levites, by the hand of Ithamar, son to Aaron the priest.

These also are the generations of Aaron and Moses in the day that the LORD spake with Moses in mount Sinai. And these are the names of the sons of Aaron; Nadab the firstborn, and Abihu, Eleazar, and Ithamar. These are the names of the sons of Aaron, the priests which were anointed, whom he consecrated to minister in the priest's office. And Nadab and Abihu died before the LORD, when they offered strange fire before the LORD, in the wilderness of Sinai, and they had no children: and Eleazar and Ithamar ministered in the priest's office in the sight of Aaron their father. And the LORD spake unto Moses, saying, Bring the tribe of Levi near, and present them before Aaron the priest, that they may minister unto him. And they shall keep his charge, and the charge of the whole congregation before the tabernacle of the congregation, to do the service of the tabernacle. And they shall keep all the instruments of the tabernacle of the congregation, and the charge of the children of Israel, to do the service of the tabernacle. And thou shalt give the Levites unto Aaron and to his sons: they are wholly given unto him out of the children of Israel. And thou shalt appoint Aaron and his sons, and they shall wait on their priest's office: and the stranger that cometh nigh shall be put to death.

And when Aaron and his sons have made an end of covering the sanctuary, and all the vessels of the sanctuary, as the camp is to set forward; after that, the sons of Kohath shall come to bear it: but they shall not touch any holy thing, lest they die. These things are the burden of the sons of Kohath in the tabernacle of the congregation. And to the office of Eleazar the son of Aaron the priest pertaineth the oil for the light, and the sweet incense, and the daily meat offering, and the anointing oil, and the oversight of all the tabernacle, and of all that therein is, in the sanctuary, and in the vessels thereof. And the LORD spake unto Moses and unto Aaron saying, Cut ye not off the tribe of the families of the Kohathites from among the Levites: But thus do unto them, that they may live, and not die, when they approach unto the most holy things: Aaron and his sons shall go in, and appoint them every one to his service and to his burden: But they shall not go in to see when the holy things are covered, lest they die. And the LORD spake unto Moses, saying, Take also the sum of the sons of Gershon, throughout the houses of their fathers, by their families; From thirty years old and upward until fifty years old shalt thou number them; all that enter in to perform the service, to do the work in the tabernacle of the congregation. This is the service of the families of the Gershonites, to serve, and for burdens: And they shall bear the curtains of the tabernacle, and the tabernacle of the congregation, his covering, and the covering of the badgers' skins that is above upon it, and the hanging for the door of the tabernacle of the congregation, And the hangings of the court, and the hanging for the door of the gate of the court, which is by the tabernacle and by the altar round about, and their cords, and all the instruments of their service, and all that is made for them: so shall they serve. At the appointment of Aaron and his sons shall be all the service of the sons of the Gershonites, in all their burdens, and in all their service: and ye shall appoint unto them in charge all their burdens. This is the service of the families of the sons of Gershon in the tabernacle of the congregation: and their charge shall be under the hand of Ithamar the son of Aaron the priest. As for the sons of Merari, thou shalt number them after their families, by the house of their fathers; From thirty years old and upward even unto fifty years old shalt thou number them, every one that entereth into the service, to do the work of the tabernacle of the congregation. And this is the charge of their burden, according to all their service in the tabernacle of the congregation; the boards of the tabernacle, and the bars thereof, and the pillars thereof, and sockets thereof, And the pillars of the court round about, and their sockets, and their pins, and their cords, with all their instruments, and with all their service: and by name ye shall reckon the instruments of the charge of their burden. This is the service of the families of the sons of Merari, according to all their service, in the tabernacle of the congregation, under the hand of Ithamar the son of Aaron the priest.

So when David was old and full of days, he made Solomon his son king over Israel. And he gathered together all the princes of Israel, with the priests and the Levites. Now the Levites were numbered from the age of thirty years and upward: and their number by their polls, man by man, was thirty and eight thousand. Of which, twenty and four thousand were to set forward the work of the house of the LORD; and six thousand were officers and judges: Moreover four thousand were porters; and four thousand praised the LORD with the instruments which I made, said David, to praise therewith. And David divided them into courses among the sons of Levi, namely, Gershon, Kohath, and Merari. Of the Gershonites were, Laadan, and Shimei. The sons of Laadan; the chief was Jehiel, and Zetham, and Joel, three. The sons of Shimei; Shelomith, and Haziel, and Haran, three. These were the chief of the fathers of Laadan. And the sons of Shimei were, Jahath, Zina, and Jeush, and Beriah. These four were the sons of Shimei. And Jahath was the chief, and Zizah the second: but Jeush and Beriah had not many sons; therefore they were in one reckoning, according to their father's house. The sons of Kohath; Amram, Izhar, Hebron, and Uzziel, four. The sons of Amram; Aaron and Moses: and Aaron was separated, that he should sanctify the most holy things, he and his sons for ever, to burn incense before the LORD, to minister unto him, and to bless in his name for ever. Now concerning Moses the man of God, his sons were named of the tribe of Levi. The sons of Moses were, Gershom, and Eliezer. Of the sons of Gershom, Shebuel was the chief. And the sons of Eliezer were, Rehabiah the chief. And Eliezer had none other sons; but the sons of Rehabiah were very many. Of the sons of Izhar; Shelomith the chief. Of the sons of Hebron; Jeriah the first, Amariah the second, Jahaziel the third, and Jekameam the fourth. Of the sons of Uzziel; Micah the first and Jesiah the second. The sons of Merari; Mahli, and Mushi. The sons of Mahli; Eleazar, and Kish. And Eleazar died, and had no sons, but daughters: and their brethren the sons of Kish took them. The sons of Mushi; Mahli, and Eder, and Jeremoth, three. 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 twenty years and upward. For David said, The LORD God of Israel hath given rest unto his people, that they may dwell in Jerusalem for ever: And also unto the Levites; they shall no more carry the tabernacle, nor any vessels of it for the service thereof. For by the last words of David the Levites were numbered from twenty years old and above: 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 purifying of all holy things, and the work of the service of the house of God; Both for the shewbread, and for the fine flour for meat offering, and for the unleavened cakes, and for that which is baked in the pan, and for that which is fried, and for all manner of measure and size; And to stand every morning to thank and praise the LORD, and likewise at even: And to offer all burnt sacrifices unto the LORD in the sabbaths, in the new moons, and on the set feasts, by number, according to the order commanded unto them, continually before the LORD: And that they should keep the charge of the tabernacle of the congregation, and the charge of the holy place, and the charge of the sons of Aaron their brethren, in the service of the house of the LORD.