Hebrews 5:1-6 ESV
For every high priest chosen from among men is appointed to act on behalf of men in relation to God, to offer gifts and sacrifices for sins. He can deal gently with the ignorant and wayward, since he himself is beset with weakness. Because of this he is obligated to offer sacrifice for his own sins just as he does for those of the people. And no one takes this honor for himself, but only when called by God, just as Aaron was.
So also Christ did not exalt himself to be made a high priest, but was appointed by him who said to him,
“You are my Son,
today I have begotten you”;
as he says also in another place
ESV: English Standard Version 2016