Numbers.
Chapter 8.
The Lord told Moses, 
“Tell Aaron, ‘When you place the seven lamps on the lampstand, make sure they shine towards the front.’” 
So that's what Aaron did. He placed the lamps facing towards the front of the lampstand, as the Lord had ordered Moses. 
The lampstand was made of hammered gold from its base to the flower decorations on the top, in accordance with the design that the Lord had shown Moses. 
The Lord told Moses, 
“Separate the Levites from the other Israelites and purify them. 
This is how you will purify them. Sprinkle on them the water of purification. They are to shave off all the hair from their bodies and wash their clothes so they will be clean. 
Have them bring a young bull with its grain offering of the best flour mixed with olive oil, and you are to bring a second young bull as a sin offering. 
Take the Levites and have them stand in front of the Tent of Meeting and have all the Israelites gather there. 
When you bring the Levites to the Lord the Israelites are to place their hands upon them. 
Aaron shall present the Levites to the Lord as a wave offering from the Israelites so that they can do the Lord's work. 
The Levites are to place their hands on the heads of the bulls. One is to be sacrificed as a sin offering to the Lord, and the other as a burnt offering to set the Levites right with the Lord. 
Have the Levites stand in front of Aaron and his sons and present them to the Lord as a wave offering. 
This is how you are to separate the Levites from the rest of the Israelites, and the Levites will belong to me. 
They can come and serve at the Tent of Meeting once you've purified them and presented them as a wave offering. 
The Levites have been completely given over to me by the Israelites. I have accepted them as mine in place of all the firstborn sons of the Israelites. 
Every firstborn male in Israel belongs to me, both human and animal. I reserved them for myself at the time when I killed all the firstborn in Egypt. 
I have taken the Levites in place of all the firstborn sons of the Israelites. 
Of all the Israelites, the Levites are a gift from me to Aaron and his sons to serve the Israelites at the Tent of Meeting, and on their behalf to set them right, so that nothing bad will happen to them when they come to the sanctuary.” 
Moses, Aaron, and all the Israelites did everything that the Lord had ordered Moses that they should do regarding the Levites. 
The Levites purified themselves and washed their clothes. Then Aaron presented them as a wave offering to the Lord. Aaron also presented the sacrifice to make them right with the Lord so they would be clean. 
Afterwards the Levites came to perform their service at the Tent of Meeting under the direction of Aaron and his sons. They followed all the instructions regarding the Levites that the Lord had given to Moses. 
The Lord told Moses, 
“This rule applies to the Levites. Those twenty-five or older shall serve at the Tent of Meeting. 
However, once they reach the age of fifty they need to retire from the work and won't serve any longer. 
They can still help their fellow Levites in their assignments, but they are not to do the actual work themselves. These are the arrangements in the case of the Levites.” 
