Augustine of Hippo

Here he is speaking not just of bishops and of presbyters (who are now priests in the church) but of all Christians. For just as we call all of them Christs by reason of their mystical chrism, we call them all priests insomuch as they are members of the one Priest. Peter speaks of them as a "chosen race, a royal priesthood." Surely, too, this text implies, however briefly and incidentally, that Christ is God. The words "priests of God and Christ" mean priests of the Father and Son, even though it was in his servant form that Christ was both made Son of man and also ordained a priest forever according to the order of Melchizedek.