If the Holy Spirit did not exist in the one who is the father and teacher of us all, when he ascended to that holy throne and gave peace to all of you, you would not have been able to reply to him with one voice: "and with your spirit." That is why you are able to say these words not only when he ascends to the altar but also when he converses with you or prays for you; and when he stand at that holy table and is on the point of offering that fearful sacrifice, it is then that you as initiated ones know that he does not touch the offerings before he has implored for you the grace of the Lord or before you have replied: "And with your spirit." This response reminds you that the one who is there does nothing by himself and that the gifts that are expected are in no way the works of man, but it is the grace of the Spirit that has descended on all of you that brings about this mystical sacrifice. There is no doubt that a man is present there, but it is God who acts through him.
St. John Chrysostom