Reply Obj. 1: This decree of Pope Leo, concerning the celebration of Baptism at two seasons, is to be understood "with the exception of the danger of death" (which is always to be feared in children) as stated above.
Reply Obj. 2: This decree concerning the Jews was for a safeguard to the Church, lest they corrupt the faith of simple people, if they be not fully converted. Nevertheless, as the same passage reads further on, "if within the appointed time they are threatened with danger of sickness, they should be baptized."
Reply Obj. 3: Baptism, by the grace which it bestows, removes not only past sins, but hinders the commission of future sins. Now this is the point to be considered—that men may not sin: it is a secondary consideration that their sins be less grievous, or that their sins be washed away, according to 1 John 2:1, 2: "My little children, these things I write to you, that you may not sin. But if any man sin, we have an advocate with the Father, Jesus Christ the just; and He is the propitiation for our sins." _______________________
FOURTH ARTICLE [III, Q. 68, Art. 4]
Whether Sinners Should Be Baptized?
Objection 1: It seems that sinners should be baptized. For it is written (Zech. 13:1): "In that day there shall be a fountain open to the House of David, and to the inhabitants of Jerusalem: for the washing of the sinner and of the unclean woman": and this is to be understood of the fountain of Baptism. Therefore it seems that the sacrament of Baptism should be offered even to sinners.
Obj. 2: Further, our Lord said (Matt. 9:12): "They that are in health need not a physician, but they that are ill." But they that are ill are sinners. Therefore since Baptism is the remedy of Christ the physician of our souls, it seems that this sacrament should be offered to sinners.
Obj. 3: Further, no assistance should be withdrawn from sinners. But sinners who have been baptized derive spiritual assistance from the very character of Baptism, since it is a disposition to grace. Therefore it seems that the sacrament of Baptism should be offered to sinners.
On the contrary, Augustine says (Serm. clxix): "He Who created thee without thee, will not justify thee without thee." But since a sinner's will is ill-disposed, he does not co-operate with God. Therefore it is useless to employ Baptism as a means of justification.
I answer that, A man may be said to be a sinner in two ways. First, on account of the stain and the debt of punishment incurred in the past: and on sinners in this sense the sacrament of Baptism should be conferred, since it is instituted specially for this purpose, that by it the uncleanness of sin may be washed away, according to Eph. 5:26: "Cleansing it by the laver of water in the word of life."