“The supreme power of the priestly office is the power of consecrating...Indeed, it is equal to that of Jesus Christ...When the priest pronounces the tremendous words of consecration, he reaches up into the heavens, brings Christ down from His throne, and places Him upon our altar to be offered up again as the Victim for the sins of man...Indeed it is greater even than the power of the Virgin Mary [who is said to be all but almighty herself]...The priest speaks and lo! Christ, the eternal and omnipotent God, bows his head in humble obedience to the priest's command. ” - (John A. O'Brien, Ph.D., LL.D., The Faith of Millions, 255-256 , O'Brien. Nihtt obstat: Rev. Lawrence Gollner, Censor Librorum Imprimatur: Leo A. Pursley, Bishop of Fort Wayne,-South Bend, March 16, 1974We see this quote thrown at us often, and what did Fr. O'Brien mean by these words? Quite simply, when the priest consecrates the Eucharist he is obeying the command from Jesus Christ to "Do this..." and when he "does this..." then that which was mere bread, Jesus comes down out of Heaven and changes the substance of the bread into the substance of Himself. The substance of that which was mere wine becomes the substance of His Most Precious Blood. The "humble obedience" which Fr. O'Brien refers to is God remaining consistent to His own command. If God did not "obey" the priest's command then the command of Jesus telling our first priests to "do this..." becomes a lie, because if God does not "obey" then when the priest holds up the Sacred Host and/or Sacred Chalice and declares "this IS My body..." and "this IS My blood..." it would be a lie - and that would make Jesus' command to them meaningless and also a lie.
"How this ['And he was carried in his own hands'] should be understood literally of David, we cannot discover; but we can discover how it is meant of Christ. FOR CHRIST WAS CARRIED IN HIS OWN HANDS, WHEN, REFERRING TO HIS OWN BODY, HE SAID: 'THIS IS MY BODY.' FOR HE CARRIED THAT BODY IN HIS HANDS." (St. Augustine, Psalms 33:1:10) This quote and more from St. Augustine found here: Was St. Augustine Catholic?