Thirdly, because last words, chiefly such as are spoken by departing friends, are committed most deeply to memory; since then especially affection for friends is more enkindled, and the things which affect us most are impressed the deepest in the soul. Consequently, since, as Pope Alexander I says, "among sacrifices there can be none greater than the body and blood of Christ, nor any more powerful oblation"; our Lord instituted this sacrament at His last parting with His disciples, in order that it might be held in the greater veneration. And this is what Augustine says (Respons. ad Januar. i): "In order to commend more earnestly the death of this mystery, our Saviour willed this last act to be fixed in the hearts and memories of the disciples whom He was about to quit for the Passion."
Reply Obj. 1: We are nourished from the same things of which we are made, but they do not come to us in the same way; for those out of which we are made come to us through generation, while the same, as nourishing us, come to us through being eaten. Hence, as we are new-born in Christ through Baptism, so through the Eucharist we eat Christ.
Reply Obj. 2: The Eucharist is the perfect sacrament of our Lord's Passion, as containing Christ crucified; consequently it could not be instituted before the Incarnation; but then there was room for only such sacraments as were prefigurative of the Lord's Passion.
Reply Obj. 3: This sacrament was instituted during the supper, so as
in the future to be a memorial of our Lord's Passion as accomplished.
Hence He said expressively: "As often as ye shall do these things"
[*Cf. Canon of the Mass], speaking of the future.
Reply Obj. 4: The institution responds to the order of intention. But the sacrament of the Eucharist, although after Baptism in the receiving, is yet previous to it in intention; and therefore it behooved to be instituted first. Or else it can be said that Baptism was already instituted in Christ's Baptism; hence some were already baptized with Christ's Baptism, as we read in John 3:22. _______________________
SIXTH ARTICLE [III, Q. 73, Art. 6]
Whether the Paschal Lamb Was the Chief Figure of This Sacrament?
Objection 1: It seems that the Paschal Lamb was not the chief figure of this sacrament, because (Ps. 109:4) Christ is called "a priest according to the order of Melchisedech," since Melchisedech bore the figure of Christ's sacrifice, in offering bread and wine. But the expression of likeness causes one thing to be named from another. Therefore, it seems that Melchisedech's offering was the principal figure of this sacrament.
Obj. 2: Further, the passage of the Red Sea was a figure of Baptism, according to 1 Cor. 10:2: "All . . . were baptized in the cloud and in the sea." But the immolation of the Paschal Lamb was previous to the passage of the Red Sea, and the Manna came after it, just as the Eucharist follows Baptism. Therefore the Manna is a more expressive figure of this sacrament than the Paschal Lamb.
Obj. 3: Further, the principal power of this sacrament is that it brings us into the kingdom of heaven, being a kind of "viaticum." But this was chiefly prefigured in the sacrament of expiation when the "high-priest entered once a year into the Holy of Holies with blood," as the Apostle proves in Heb. 9. Consequently, it seems that that sacrifice was a more significant figure of this sacrament than was the Paschal Lamb.