Exodus 29:9

Therefore thou and thy sons with thee shall keep your priest’s office for everything of the altar, and within the vail; and ye shall serve: I have given your priest’s office unto you as a service of gift: and the stranger that cometh nigh shall be put to death.

For the LORD thy God hath chosen him out of all thy tribes, to stand to minister in the name of the LORD, him and his sons for ever.

And ye shall not go out of the door of the tabernacle of the congregation in seven days, until the days of your consecration be at an end: for seven days shall he consecrate you.

And thou shalt anoint them, as thou didst anoint their father, that they may minister unto me in the priest’s office: for their anointing shall surely be an everlasting priesthood throughout their generations.

And he hath brought thee near to him, and all thy brethren the sons of Levi with thee: and seek ye the priesthood also?

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.

To be a memorial unto the children of Israel, that no stranger, which is not of the seed of Aaron, come near to offer incense before the LORD; that he be not as Korah, and as his company: as the LORD said to him by the hand of Moses.

And he shall have it, and his seed after him, even the covenant of an everlasting priesthood; because he was zealous for his God, and made an atonement for the children of Israel.

And there came out a fire from the LORD, and consumed the two hundred and fifty men that offered incense.

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.

And take thou unto thee Aaron thy brother, and his sons with him, from among the children of Israel, that he may minister unto me in the priest’s office, even Aaron, Nadab and Abihu, Eleazar and Ithamar, Aaron’s sons.

Called of God an high priest after the order of Melchisedec.