Albert Barnes Commentary Hebrews 10:21

"and [having] a great priest over the house of God;" — Hebrews 10:21 (ASV)

And having an High Priest over the house of God. Over the spiritual house of God; that is, the church. Compare to Hebrews 3:1-6.

Under the Jewish dispensation, there was a great high priest, and the same is true under the Christian dispensation.

This the apostle had shown at length in the previous part of the epistle. The idea here is that, as under the former dispensation it was regarded as a privilege that the people of God might have access to the mercy-seat by means of the high priest, so it is true, in a much higher sense, that we may now have access to God through our greater and more glorious High Priest.