'Priesthood' in the Bible

You shall appoint Aaron and his sons, and they shall keep their priesthood. The stranger who comes near shall be put to death."

and that he has brought you near, and all your brothers the sons of Levi with you? and do you seek the priesthood also?

Yahweh said to Aaron, "You and your sons and your fathers' house with you shall bear the iniquity of the sanctuary; and you and your sons with you shall bear the iniquity of your priesthood.

You and your sons with you shall keep your priesthood for everything of the altar, and for that within the veil; and you shall serve: I give you the priesthood as a service of gift: and the stranger who comes near shall be put to death."

and it shall be to him, and to his seed after him, the covenant of an everlasting priesthood; because he was jealous for his God, and made atonement for the children of Israel.'"