Thomas Aquinas

“ Dogm.: "If the soul leans towards sin, it is burdened rather than purified from partaking of the Eucharist." Hence, in him who is conscious of mortal sin, this sacrament does not cause the forgiveness of sin. ”

“ As Christ's Passion benefits all, for the forgiveness of sin and the attaining of grace and glory, whereas it produces no effect except in those who are united with Christ's Passion through faith and charity, so likewise this sacrifice, which is the memorial of our Lord's Passion, has no effect except in those who are united with this sacrament through faith and charity. ”

“ Hence it is due to the efficacy of its power, that even from desire thereof a man procures grace whereby he is enabled to lead the spiritual life. It remains, then, that when the sacrament itself is really received, grace is increased, and the spiritual life perfected: yet in different fashion from the sacrament of Confirmation, in which grace is increased and perfected for resisting the outward assaults of Christ's enemies. ”

“ Baptism is spiritual generation, which is a transition from spiritual non-being into spiritual being, and is given by way of ablution. Consequently, in both respects he who is conscious of mortal sin does not improperly approach Baptism. But in this sacrament man receives Christ within himself by way of spiritual nourishment, which is unbecoming to one that lies dead in his sins. ”

“ But because this union is the effect of charity, from the fervor of which man obtains forgiveness, not only of guilt but also of punishment, hence it is that as a consequence, and by concomitance with the chief effect, man obtains forgiveness of the punishment, not indeed of the entire punishment, but according to the measure of his devotion and fervor. ”

“ If therefore this sacrament were to produce its effects in others besides the recipients, a man might happen to acquire grace and glory and forgiveness of sin without doing or receiving anything himself, through another receiving or offering this sacrament. ”

“ Even charity of itself keeps man from sin, according to Rom. 13:10: "The love of our neighbor worketh no evil": but it is due to the mutability of free-will that a man sins after possessing charity, just as after receiving this sacrament.
Reply to Objection 3: Although this sacrament is not ordained directly to lessen the fomes, yet it does lessen it as a consequence, inasmuch as it increases charity, because, as Augustine says ( [4629] Q [83] ) , "the increase of charity is the lessening of concupiscence." But it directly strengthens man's heart in good; whereby he is also preserved from sin. ”

“ I answer that, This sacrament is both a sacrifice and a sacrament. it has the nature of a sacrifice inasmuch as it is offered up; and it has the nature of a sacrament inasmuch as it is received. And therefore it has the effect of a sacrament in the recipient, and the effect of a sacrifice in the offerer, or in them for whom it is offered. ”

“ Now this sacrament preserves man from sin in both of these ways. For, first of all, by uniting man with Christ through grace, it strengthens his spiritual life, as spiritual food and spiritual medicine, according to Ps. 103:5: " (That) bread strengthens [Vulg.: 'may strengthen'] man's heart." Augustine likewise says (Tract. xxvi in Joan.) : "Approach without fear; it is bread, not poison." Secondly, inasmuch as it is a sign of Christ's Passion, whereby the devils are conquered, it repels all the assaults of demons. ”

“ 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." ”