Numbers 8:15

The families of the Gershonites shall pitch behind the tabernacle westward. And the chief of the house of the father of the Gershonites shall be Eliasaph the son of Lael. And the charge of the sons of Gershon in the tabernacle of the congregation shall be the tabernacle, and the tent, the covering thereof, and the hanging for the door of the tabernacle of the congregation, And the hangings of the court, and the curtain for the door of the court, which is by the tabernacle, and by the altar round about, and the cords of it for all the service thereof. And of Kohath was the family of the Amramites, and the family of the Izeharites, and the family of the Hebronites, and the family of the Uzzielites: these are the families of the Kohathites. In the number of all the males, from a month old and upward, were eight thousand and six hundred, keeping the charge of the sanctuary. The families of the sons of Kohath shall pitch on the side of the tabernacle southward. And the chief of the house of the father of the families of the Kohathites shall be Elizaphan the son of Uzziel. And their charge shall be the ark, and the table, and the candlestick, and the altars, and the vessels of the sanctuary wherewith they minister, and the hanging, and all the service thereof. And Eleazar the son of Aaron the priest shall be chief over the chief of the Levites, and have the oversight of them that keep the charge of the sanctuary. Of Merari was the family of the Mahlites, and the family of the Mushites: these are the families of Merari. And those that were numbered of them, according to the number of all the males, from a month old and upward, were six thousand and two hundred. And the chief of the house of the father of the families of Merari was Zuriel the son of Abihail: these shall pitch on the side of the tabernacle northward. And under the custody and charge of the sons of Merari shall be the boards of the tabernacle, and the bars thereof, and the pillars thereof, and the sockets thereof, and all the vessels thereof, and all that serveth thereto, And the pillars of the court round about, and their sockets, and their pins, and their cords.

From thirty years old and upward even until fifty years old, all that enter into the host, to do the work in the tabernacle of the congregation. This shall be the service of the sons of Kohath in the tabernacle of the congregation, about the most holy things: And when the camp setteth forward, Aaron shall come, and his sons, and they shall take down the covering vail, and cover the ark of testimony with it: And shall put thereon the covering of badgers' skins, and shall spread over it a cloth wholly of blue, and shall put in the staves thereof. And upon the table of showbread they shall spread a cloth of blue, and put thereon the dishes, and the spoons, and the bowls, and covers to cover withal: and the continual bread shall be thereon: And they shall spread upon them a cloth of scarlet, and cover the same with a covering of badgers' skins, and shall put in the staves thereof. And they shall take a cloth of blue, and cover the candlestick of the light, and his lamps, and his tongs, and his snuffdishes, and all the oil vessels thereof, wherewith they minister unto it: And they shall put it and all the vessels thereof within a covering of badgers' skins, and shall put it upon a bar. And upon the golden altar they shall spread a cloth of blue, and cover it with a covering of badgers' skins, and shall put to the staves thereof: And they shall take all the instruments of ministry, wherewith they minister in the sanctuary, and put them in a cloth of blue, and cover them with a covering of badgers' skins, and shall put them on a bar: And they shall take away the ashes from the altar, and spread a purple cloth thereon: And they shall put upon it all the vessels thereof, wherewith they minister about it, even the censers, the fleshhooks, and the shovels, and the basins, all the vessels of the altar; and they shall spread upon it a covering of badgers' skins, and put to the staves of it. 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.

And Aaron shall offer the Levites before the LORD for an offering of the children of Israel, that they may execute the service of the LORD.

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.

The four and twentieth to Romamtiezer, he, his sons, and his brethren, were twelve.