But do ye all, as many as are made glad, by the gift of regeneration, and make your boast of that saving renewal, show me, after the sacramental grace, the change in your ways that should follow it, and make known by the purity of your conversation the difference effected by your transformation for the better. For of those things which are before our eyes nothing is altered: the characteristics of the body remain unchanged, and the mould of the visible nature is nowise different. But there is certainly need of some manifest proof, by which we may recognize the new-born man, discerning by clear tokens the new from the old. And these I think are to be found in the intentional motions of the soul, whereby it separates itself from its old customary life, and enters on a newer way of conversation, and will clearly teach those acquainted with it that it has become something different from its former self, bearing in it no token by which the old self was recognized. This, if you be persuaded by me, and keep my words as a law, is the mode of the transformation. The man that was before Baptism was wanton, covetous, grasping at the goods of others, a reviler, a liar, a slanderer, and all that is kindred with these things, and consequent from them. Let him now become orderly, sober, content with his own possessions, and imparting from them to those in poverty, truthful, courteous, affable— in a word, following every laudable course of conduct. For as darkness is dispelled by light, and black disappears as whiteness is spread over it, so the old man also disappears when adorned with the works of righteousness. You see how Zacchæus also by the change of his life slew the publican, making fourfold restitution to those whom he had unjustly damaged, and the rest he divided with the poor— the treasure which he had before got by ill means from the poor whom he oppressed. The Evangelist Matthew, another publican, of the same business with Zacchæus, at once after his call changed his life as if it had been a mask. Paul was a persecutor, but after the grace bestowed on him an Apostle, bearing the weight of his fetters for Christ's sake, as an act of amends and repentance for those unjust bonds which he once received from the Law, and bore for use against the Gospel. Such ought you to be in your regeneration: so ought you to blot out your habits that tend to sin; so ought the sons of God to have their conversation: for after the grace bestowed we are called His children. And therefore we ought narrowly to scrutinize our Father's characteristics, that by fashioning and framing ourselves to the likeness of our Father, we may appear true children of Him Who calls us to the adoption according to grace. For the bastard and the supposititious son, who belies his father's nobility in his deeds, is a sad reproach. Therefore also, methinks, it is that the Lord Himself, laying down for us in the Gospels the rules of our life, uses these words to His disciples, “Do good to them that hate you, pray for them that despitefully use you and persecute you; that you may be the children of your Father which is in heaven: for He makes His sun to rise on the evil and on the good, and sends rain on the just and on the unjust.” For then He says they are sons when in their own modes of thought they are fashioned in loving kindness towards their kindred, after the likeness of the Father's goodness.
Therefore, also, it is that after the dignity of adoption the devil plots more vehemently against us, pining away with envious glance, when he beholds the beauty of the new-born man, earnestly tending towards that heavenly city, from which he fell: and he raises up against us fiery temptations, seeking earnestly to despoil us of that second adornment, as he did of our former array. But when we are aware of his attacks, we ought to repeat to ourselves the apostolic words, “As many of us as were baptized into Christ were baptized into His death.” Now if we have been conformed to His death, sin henceforth in us is surely a corpse, pierced through by the javelin of Baptism, as that fornicator was thrust through by the zealous Phinehas. Flee therefore from us, ill-omened one! For it is a corpse you seek to despoil, one long ago joined to you, one who long since lost his senses for pleasures. A corpse is not enamoured of bodies, a corpse is not captivated by wealth, a corpse slanders not, a corpse lies not, snatches not at what is not its own, reviles not those who encounter it. My way of living is regulated for another life: I have learned to despise the things that are in the world, to pass by the things of earth, to hasten to the things of heaven, even as Paul expressly testifies, that the world is crucified to him, and he to the world. These are the words of a soul truly regenerated: these are the utterances of the newly-baptized man, who remembers his own profession, which he made to God when the sacrament was administered to him, promising that he would despise for the sake of love towards Him all torment and all pleasure alike.
And now we have spoken sufficiently for the holy subject of the day, which the circling year brings to us at appointed periods. We shall do well in what remains to end our discourse by turning it to the loving Giver of so great a boon, offering to Him a few words as the requital of great things. For You verily, O Lord, are the pure and eternal fount of goodness, Who justly turned away from us, and in loving kindness had mercy upon us. You hated, and were reconciled; You cursed, and blessed; You banished us from Paradise, and recalled us; You stripped off the fig-tree leaves, an unseemly covering, and put upon us a costly garment; You opened the prison, and released the condemned; You sprinkled us with clean water, and cleanse us from our filthiness. No longer shall Adam be confounded when called by You, nor hide himself, convicted by his conscience, cowering in the thicket of Paradise. Nor shall the flaming sword encircle Paradise around, and make the entrance inaccessible to those that draw near; but all is turned to joy for us that were the heirs of sin: Paradise, yea, heaven itself may be trodden by man: and the creation, in the world and above the world, that once was at variance with itself, is knit together in friendship: and we men are made to join in the angels' song, offering the worship of their praise to God. For all these things then let us sing to God that hymn of joy, which lips touched by the Spirit long ago sang loudly: “Let my soul be joyful in the Lord: for He has clothed me with a garment of salvation, and has put upon me a robe of gladness: as on a bridegroom He has set a mitre upon me, and as a bride has He adorned me with fair array.” And verily the Adorner of the bride is Christ, Who is, and was, and shall be, blessed now and for evermore. Amen.
Source: On the Baptism of Christ (Sermon for the Day of Lights) (New Advent)