Hebrews 5:4-6

4And no one takes this honor on himself, but he receives it when called by God, just as Aaron was.

5In the same way, Christ did not take on himself the glory of becoming a high priest. But God said to him, “You are my Son; today I have become your Father.” Psalm 2:7

6And he says in another place, “You are a priest forever, in the order of Melchizedek.” Psalm 110:4