Hebrews 10:21

And [having an] high priest over the house of God. The church of God, over which Christ is as prophet, priest, and King, and as the Son and owner of it; [See comments on Hebrews 3:6];

[See comments on Hebrews 4:14]. In the Greek text it is, "a great priest"; so the Messiah is called by the Targum on Zechariah 6:12 כהן רב, "a great priest", as he is; even a great high priest, as in Hebrews 4:14, and greater than Aaron, and any of his sons.