22 And whilst they were eating, Jesus took bread; and blessing, broke, and gave to them, and said: Take ye. This is my body.
Bede: When the rites of the old Passover were finished, He passed to the new, in order, that is, to substitute the Sacrament of His own Body and Blood, for the flesh and blood of the lamb. Wherefore there follows: “And as they did eat, Jesus took bread”; that is, in order to shew that He, Himself, is that person to whom the Lord swore, “Thou art a Priest forever after the order of Melchizedec” [Ps 110:4].
Bede: He Himself also breaks the bread, which He gives to His disciples, to shew that the breaking of His Body was to take place, not against His Will, nor without His intervention; He also blessed it, because He with the Father and the Holy Spirit filled His human nature, which He took upon Him in order to suffer, with the grace of Divine power. He blessed bread and brake it, because He deigned to subject to death His manhood, which He had taken upon Him in such a way as to shew that there was within it the power of Divine immortality, and to teach them that therefore He would the more quickly raise it from the dead.
Theophylact: The bread is not a mere figure of the Body of Christ, but is changed into the very Body of Christ. For the Lord said, “The bread which I give you is My Flesh” [John 6:51]. But the Flesh of Christ is veiled from our eyes on account of our weakness, for bread and wine are things to which we are accustomed, if however we saw flesh and blood we could not bear to take them. For this reason the Lord bending Himself to our weakness keeps the forms of bread and wine, but changes the bread and wine into the reality of His Body and Blood.
Chrysostom: Even now also that Christ is close to us; He Who prepared that table, Himself also consecrates it. For it is not man who makes the offerings to be the Body and Blood of Christ, but Christ Who was crucified for us. The words are spoken by the mouth of the Priest, and are consecrated by the power and the grace of God. By this word which He spoke, “This is My Body,” the offerings are consecrated; and as that word which says, “Increase and multiply, and fill the earth” [Gen 1:28], was sent forth but once, yet has its effect throughout all time, when nature does the work of generation; so also that voice was spoken once, yet gives confirmation to the Sacrifice through all the tables of The Church even to this day, even to His advent.
Scripture from the Douay-Rheims Bible. Commentary from St. Thomas Aquinas, Catena Aurea, Vol. II (London: Rivington, 1842).