Hebrews 5:4-5
And no one takes this honourable office upon himself, but only accepts it when called to it by God, as Aaron was.
Hebrews 5:10
For God Himself addresses Him as a High Priest for ever, belonging to the order of Melchizedek.
Hebrews 7:11-14
Now if the crowning blessing was attainable by means of the Levitical priesthood--for as resting on this foundation the people received the Law, to which they are still subject-- what further need was there for a Priest of a different kind to be raised up belonging to the order of Melchizedek instead of being said to belong to the order of Aaron?
Hebrews 7:23-28
And they have been appointed priests many in number, because death prevents their continuance in office: