Hebrews 5:4-5

5:4 And no one assumes this honor on his own initiative, but only when called to it by God, as in fact Aaron was. 5:5 So also Christ did not glorify himself in becoming high priest, but the one who glorified him was God, who said to him, “You are my Son! Today I have fathered you,”

Hebrews 5:10

5:10 and he was designated by God as high priest in the order of Melchizedek.