Hebrews 5:4

5:4 And no one assumes this honor on his own initiative, but only when called to it by God, as in fact Aaron was.

Exodus 28:1

The Clothing of the Priests

28:1 “And you, bring near to you your brother Aaron and his sons with him from among the Israelites, so that they may minister as my priests – Aaron, Nadab and Abihu, Eleazar and Ithamar, Aaron’s sons.

Numbers 16:10-11

16:10 He has brought you near and all your brothers, the sons of Levi, with you. Do you now seek the priesthood also? 16:11 Therefore you and all your company have assembled together against the Lord! And Aaron – what is he that you murmur against him?”

Numbers 17:3-10

17:3 You must write Aaron’s name on the staff of Levi; for one staff is for the head of every tribe. 17:4 You must place them in the tent of meeting before the ark of the covenant where I meet with you. 17:5 And the staff of the man whom I choose will blossom; so I will rid myself of the complaints of the Israelites, which they murmur against you.”

17:6 So Moses spoke to the Israelites, and each of their leaders gave him a staff, one for each leader, according to their tribes – twelve staffs; the staff of Aaron was among their staffs. 17:7 Then Moses placed the staffs before the Lord in the tent of the testimony.

17:8 On the next day Moses went into the tent of the testimony – and the staff of Aaron for the house of Levi had sprouted, and brought forth buds, and produced blossoms, and yielded almonds! 17:9 So Moses brought out all the staffs from before the Lord to all the Israelites. They looked at them, and each man took his staff.

The Memorial

17:10 The Lord said to Moses, “Bring Aaron’s staff back before the testimony to be preserved for a sign to the rebels, so that you may bring their murmurings to an end before me, that they will not die.”

Numbers 18:7

18:7 But you and your sons with you are responsible for your priestly duties, for everything at the altar and within the curtain. And you must serve. I give you the priesthood as a gift for service; but the unauthorized person who approaches must be put to death.”

Numbers 18:21-26

18:21 See, I have given the Levites all the tithes in Israel for an inheritance, for their service which they perform – the service of the tent of meeting. 18:22 No longer may the Israelites approach the tent of meeting, or else they will bear their sin and die. 18:23 But the Levites must perform the service of the tent of meeting, and they must bear their iniquity. It will be a perpetual ordinance throughout your generations that among the Israelites the Levites have no inheritance. 18:24 But I have given to the Levites for an inheritance the tithes of the Israelites that are offered to the Lord as a raised offering. That is why I said to them that among the Israelites they are to have no inheritance.”

Instructions for the Levites

18:25 The Lord spoke to Moses: 18:26 “You are to speak to the Levites, and you must tell them, ‘When you receive from the Israelites the tithe that I have given you from them as your inheritance, then you are to offer up from it as a raised offering to the Lord a tenth of the tithe.