Now as to both of these it belongs to this sacrament to cause the attaining of eternal life. Because it was by His Passion that Christ opened to us the approach to eternal life, according to Heb. 9:15: "He is the Mediator of the New Testament; that by means of His death . . . they that are called may receive the promise of eternal inheritance." Accordingly in the form of this sacrament it is said: "This is the chalice of My blood, of the New and Eternal Testament."
In like manner the refreshment of spiritual food and the unity denoted by the species of the bread and wine are to be had in the present life, although imperfectly, but perfectly in the state of glory. Hence Augustine says on the words, "My flesh is meat indeed" (John 6:56): "Seeing that in meat and drink, men aim at this, that they hunger not nor thirst, this verily nought doth afford save only this meat and drink which maketh them who partake thereof to be immortal and incorruptible, in the fellowship of the saints, where shall be peace, and unity, full and perfect."
Reply Obj. 1: As Christ's Passion, in virtue whereof this sacrament is accomplished, is indeed the sufficient cause of glory, yet not so that we are thereby forthwith admitted to glory, but we must first "suffer with Him in order that we may also be glorified" afterwards "with Him" (Rom. 8:17), so this sacrament does not at once admit us to glory, but bestows on us the power of coming unto glory. And therefore it is called "Viaticum," a figure whereof we read in 3 Kings 19:8: "Elias ate and drank, and walked in the strength of that food forty days and forty nights unto the mount of God, Horeb."
Reply Obj. 2: Just as Christ's Passion has not its effect in them who are not disposed towards it as they should be, so also they do not come to glory through this sacrament who receive it unworthily. Hence Augustine (Tract. xxvi in Joan.), expounding the same passage, observes: "The sacrament is one thing, the power of the sacrament another. Many receive it from the altar . . . and by receiving" . . . die . . . Eat, then, spiritually the heavenly "bread, bring innocence to the altar." It is no wonder, then, if those who do not keep innocence, do not secure the effect of this sacrament.
Reply Obj. 3: That Christ is received under another species belongs to the nature of a sacrament, which acts instrumentally. But there is nothing to prevent an instrumental cause from producing a more mighty effect, as is evident from what was said above (Q. 77, A. 3, ad 3). _______________________
THIRD ARTICLE [III, Q. 79, Art. 3]
Whether the Forgiveness of Mortal Sin Is an Effect of This Sacrament?
Objection 1: It seems that the forgiveness of mortal sin is an effect of this sacrament. For it is said in one of the Collects (Postcommunion, Pro vivis et defunctis): "May this sacrament be a cleansing from crimes." But mortal sins are called crimes. Therefore mortal sins are blotted out by this sacrament.
Obj. 2: Further, this sacrament, like Baptism, works by the power of Christ's Passion. But mortal sins are forgiven by Baptism, as stated above (Q. 69, A. 1). Therefore they are forgiven likewise by this sacrament, especially since in the form of this sacrament it is said: "Which shall be shed for many unto the forgiveness of sins."
Obj. 3: Further, grace is bestowed through this sacrament, as stated above (A. 1). But by grace a man is justified from mortal sins, according to Rom. 3:24: "Being justified freely by His grace." Therefore mortal sins are forgiven by this sacrament.