This is the account of the family of Aaron and Moses at the time the LORD spoke with Moses on Mount Sinai.
The sons of Aaron were Nadab, the firstborn, Abihu, Eleazar, and Ithamar. These were the names of Aaron's sons—the anointed priests, chosen and ordained to serve before the LORD. But Nadab and Abihu fell dead before the LORD in the wilderness of Sinai when they offered unauthorized fire before Him. They left no sons behind, so only Eleazar and Ithamar served as priests during the lifetime of their father Aaron.
Then the LORD said to Moses:
"Bring the tribe of Levi and present them before Aaron the priest, to assist him. They are to serve under him and perform duties for the whole community at the Tent of Meeting, taking care of the furnishings and all the work of the Tabernacle. Give the Levites to Aaron and his sons; they are wholly given to him from among the Israelites. But appoint Aaron and his sons to serve as priests. Anyone else who approaches the sanctuary must be put to death."
And the LORD said further:
"I have taken the Levites from among the Israelites in place of every firstborn male who opens the womb. The Levites are Mine, for all the firstborn are Mine. When I struck down all the firstborn in Egypt, I set apart every firstborn in Israel, whether man or animal, to be Mine. I am the LORD."
So the LORD commanded Moses in the wilderness of Sinai:
"Count the Levites by their families and clans. Count every male one month old and above."
And Moses did as he was told. The sons of Levi were three: Gershon, Kohath, and Merari. From Gershon came the clans of Libni and Shimei. From Kohath came the clans of Amram, Izhar, Hebron, and Uzziel. From Merari came the clans of Mahli and Mushi. These were the families of the Levites.
The Gershonites, numbering 7,500 males a month old and above, camped to the west of the Tabernacle, behind it. Their leader was Eliasaph son of Lael. They were responsible for the care of the tabernacle itself, the tent and its coverings, the curtain at the entrance, the curtains of the courtyard, the screen for the entrance to the courtyard surrounding the tabernacle and altar, the ropes, and everything related to their use.
The Kohathites numbered 8,600 males. They camped on the south side of the Tabernacle. Their leader was Elizaphan son of Uzziel. They were responsible for the most holy things—the ark of the covenant, the table, the lampstand, the altars, the sacred utensils, the veil, and everything used in the ministry of the sanctuary. Over them stood Eleazar, son of Aaron the priest, as chief leader of the Levites, charged with the oversight of the holy things.
The Merarites numbered 6,200 males. They camped on the north side of the Tabernacle. Their leader was Zuriel son of Abihail. They were responsible for the framework of the Tabernacle—the posts, bases, crossbars, equipment, and everything connected with them, including the posts of the courtyard with their bases, tent pegs, and ropes.
Moses and Aaron and his sons camped on the east side, before the entrance to the Tent of Meeting, facing the sunrise. They were responsible for the sanctuary itself, on behalf of all Israel. Anyone else who dared to approach the sanctuary was to be put to death.
The total number of Levites counted at the LORD's command by Moses and Aaron, every male a month old and above, was 22,000.
Then the LORD said to Moses:
"Count all the firstborn males of the Israelites, a month old and above, and list their names. Take the Levites for Me in place of the firstborn of Israel, and the livestock of the Levites in place of the firstborn livestock of Israel. The Levites are Mine. I am the LORD."
So Moses counted the firstborn of Israel, just as the LORD commanded. The total number of firstborn males, one month old and above, listed by name, was 22,273.
The LORD then said:
"Take the Levites in place of the firstborn of Israel, and the livestock of the Levites in place of the livestock of Israel. But for the 273 Israelites who exceed the number of Levites, collect a ransom—five shekels for each, according to the sanctuary shekel, which weighs twenty gerahs. Give the ransom money to Aaron and his sons."
So Moses collected the ransom money from the extra 273 firstborn Israelites. He received 1,365 shekels, according to the sanctuary shekel, and gave it to Aaron and his sons, just as the LORD had commanded.