Pacian/Pacianus (310-391) was a bishop of Barcelona. One of his extant works, "Discourse on Baptism to the Faithful and the Catechumens" is pretty explicit in teaching baptismal regeneration, again showing that this view of baptism was unanimous in the earliest centuries of Christianity. Here is Rev. C.H. Collyns' translation of the discourse:
2. Learn then, dearly beloved, in what death man was placed before Baptism. Ye know that assuredly of old, how Adam was returned to his earthly origin; what condemnation imposed upon him the law of eternal death; and this death had dominion over all his posterity, as being held under this one law, over the whole race from Adam to Moses. But through Moses one only people was chosen, the seed that is of Abraham, if they had been able to keep the commands of righteousness. Meanwhile we all were held under sin, that we might eat the fruits of death: appointed to feed on husks and to keep swine, that is to filthy works, by wicked augels, whose dominion allowed us neither to do nor to know righteousness. For our very condition compelled us to obey such masters. How we were delivered from these powers and from this death, now listen.
3. When Adam sinned, (as I have mentioned,) the Lord then saying, Dust thou art, and unto dust thou shall return, he was assigned unto death. This assignment was transmitted to the whole race, for all sinned, nature herself now impelling them, as saith the Apostle, As by one man sin entered into the world, and death by sin; and so death passed upon all men, for that all have sinned. Sin therefore reigned, in whose bonds we were dragged, as it were captives unto death, death, that is, eternal. But this sin, before the time of the Law, was not even understood, as saith the Apostle, Until the Law was, sin in the world was not accounted, that is, was not seen; at the coming of the Law, it revived. For it was made manifest, that it might be seen; but to no purpose, for no one hardly kept it. For the Law said, Thou shall not commit adultery, thou shall not kill, thou shall not covet, yet concupiscence with all vices still continued. So then before the Law this sin slew man with a concealed, under the Law, with a drawn, sword. What hope therefore had man? Without the Law he perished, because he could not see sin, and under the Law, because he ran into that very sin which he saw. Who could free him from death? Hear the Apostle, O wretched man that I am! who shall deliver me from the body of this death? Grace (he saith) through our Lord Jesus Christ.
4. But what is grace? The remission of sin, that is, a free gift. For grace is a free gift. Christ therefore, coming and taking upon Him the nature of man, first presented before God this very human nature pure from the power of sin and innocent. Isaiah saith, Behold a virgin shall conceive, and bear a Son, and shall call His name Immanuel. Butter and honey shall He eat, that He may know to refuse the evil and choose the good. And of Him again, Who did no sin, neither was guile found in His mouth. Under this guardianship of innocence when Christ first undertook the defence of man in the very flesh of sin, forthwith that father of the disobedience of sin, who had once deceived our first parents, began to be excited, to be troubled, to tremble. For he was to be overcome by the loosening of that law by which alone he had retained possession of man, or could retain it. He arms himself therefore for a spiritual contest with the Immaculate, and first he attacks Him with that artifice with which he had overcome Adam in Paradise, under the pretence of dignity; and as if perplexed about His heavenly power, he saith, If Thou be the Son of God, command that these stones be made bread; that so ashamed or unwilling to conceal that He was the Son of God, He might fulfil the commands of the tempter. Behold still he is not silent, suggesting that if He would cast Himself down from above, He would be received in the hands of angels, to whom The Father had entrusted that on their hands they should bear Him up, lest by any means He should dash His foot against a stone; that so, while the Lord wished to prove that He it was of Whom the Father had given this command, He might do what the tempter urged. Last of all the serpent being now crushed, as if he were now giving up, promises Him those very kingdoms of the world, which he had taken from the first man: that so whilst the Advocate of man believes that he has overcome, He by receiving the empire (which He was to recover,) might incline towards the dignity offered by the Evil One, and so at last sin. But in all these attacks the Enemy is overcome, and destroyed by the heavenly power, as saith the Prophet unto the Lord, That thou mightest still the enemy, and the avenger. For I shall behold the heavens, the works of Thy fingers.
5. The Devil ought now to have yielded. But nevertheless he ceaseth not yet. He suborns with his wonted snares, and stimulates with rage the Scribes and Pharisees and all that band of wicked men. They, therefore, after various arts and lying devices of the heart, in which serpent-like they thought to deceive the Lord by professions of fealty, when they prevailed nothing, at last attacked Him with open violence and a most cruel kind of suffering; that so through the indignity of the thing, or the pain of punishment, He might either do or say something unrighteous, and thus destroy the human nature which He bore, and His soul be left in hell, which had one law to retain the sinner. For the sting of death is sin. Christ therefore endured, and did no sin, neither was guile found in His mouth, as we have said, not then even when He was led as a victim,. This was to conquer, to be condemned without sin! For the Devil had received over sinners the power which he claimed for himself over the Immaculate One; and thus he himself was overcome; decreeing that against the Holy One which was not allowed him by the law that he had received. Whence saith the Prophet to the Lord, That Thou mightest be justified in Thy saying, and clear when Thou art judge. And thus, as the Apostle saith, Having led principalities in triumph, Christ condemned sin in the flesh, nailing it to His Cross and blotting out the hand-writing of death. Thence it was that God left not His soul in hell, nor suffered His Holy One to see corruption. Thence it was that having trodden under-foot the stings of death He rose again on the third day in the flesh, reconciling it to God, and restoring it to immortality, having overcome and blotted out sin.
6. But if He only conquered, what conferred He on others? Hear briefly. The sin of Adam had passed on the whole race. For by one man (as saith the Apostle) sin entered into the world, and death by sin; and so death passed upon all men. Therefore also the righteousness of Christ must needs pass over to the whole race; and as Adam by sin destroyed his race, so must Christ by righteousness give life to all His race. This the Apostle urges, saying, For as by the disobedience of one, many were made sinners, so by the obedience of One shall many be made righteous. That as sin hath reigned unto death, even so might grace reign through righteousness unto eternal life.
7. Some one will here object. "But the sin of Adam deservedly passed on his posterity, because they were born of him. And are we then born of Christ, that we can be saved for His sake?" Cease to have carnal thoughts. And now shall ye see in what wise we are born of Christ as of our parent. In these last days Christ took a soul with the flesh from Mary. This He came to save. This He left not in hell. This He joined to His Spirit and made His own. And this is the marriage of the Lord, joined together to one flesh, that according to that great sacrament, might be these two in one flesh, Christ and the Church. From this marriage is born the Christian people, the Spirit of the Lord coming from above; and straightway the heavenly seed being poured upon and mingled with the substance of our souls, we grow in the bowels of our mother, and coming forth from her womb are made alive in Christ. Whence the Apostle, The first Adam was made a living soul; the last Adam was made a quickening Spirit. Thus Christ begetteth in the Church by His Priests, as says the same Apostle, For in Christ Jesus have I begotten you. And so the seed of Christ, that is, the Spirit of God produces, by the hands of the Priests, the new man conceived in the womb of our Mother, and received at the birth of the font, faith presiding over the marriage rite. For neither will he seem to be engrafted into the Church, who hath not believed, nor he to be born again of Christ, who hath not himself received the Spirit. We must believe therefore that we can be born. For so saith Philip, If thou believest . . . thou mayest. Christ therefore must be received that He may beget, for thus saith the Apostle John, As many as received Him, to them gave He power to become the sons of God. But these things cannot otherwise be fulfilled except by the Sacrament of the Laver, and of the Chrism, and of the Bishop. For by the Laver sins are washed away, by Chrism the Holy Spirit is poured out, but both these we obtain at the hand and the mouth of the Bishop. And so the whole man is born again and renewed in Christ, that like as Christ was raised up from the dead, even so we also should walk in newness of life; that is, that having laid aside the errors of our former life, the serving of idols, cruelty, fornication, wantonness, and all other vices of flesh and blood, we should through the Spirit follow new ways in Christ, faith, modesty, innocence, chastity. And as we bore the image of the earthy, so also should we bear His, Who is from Heaven, for the first man is of the earth, earthy; the Second from heaven, heavenly. This if we do, most beloved, we shall die no more. Although we be dissolved in this body, we shall live in Christ, as He Himself saith, He that believeth in Me, though he were dead, yet shall he live. We are sure indeed, and that on the testimony of the Lord, that both Abraham, and Isaac, and Jacob, and all the Saints of God are alive. For of these very men saith the Lord, They all live unto Him, for God is not the God of the dead but of the living. And the Apostle saith of himself, For to me to live is Christ, and to die is gain; I could wish to depart and be with Christ. And again, Whilst we are at home in the body, we are absent from the Lord; for we walk by faith, not by sight. This is what, we believe, dearly beloved. But if in this life only we have hope, then are we of all men the most miserable. The life of this world, cattle, and wild beasts, and birds, as yourselves see, have in common with us, or even longer. That is peculiar to man, which Christ hath given through His Spirit, that is, life, eternal; yet only if we now sin no more. For as death is gained by wickedness, is avoided by goodness; so life is lost by wickedness, is retained by goodness. For the wages of sin is death; but the gift of God is eternal life through Jesus Christ our Lord. Before all other things, my little ones, remember, that once (as we said above) all nations were given over to the princes and powers of darkness, now are set free through the victory of our Lord Jesus Christ. He it is, He it is Who redeemed us, forgiving us all sins, as saith the Apostle, blotting out the hand-writing of disobedience that was against us, and took it out of the way, nailing it to His Cross, putting off the flesh, He made a shew of the powers openly, triumphing over them in Himself. He set them free, who were bound, and burst our chains in sunder, as David had said; The Lord raiseth them that are cast down. The Lord looseth the prisoners, the Lord giveth sight to the blind. And again, Thou hast broken my bonds in sunder. I will offer to Thee the Sacrifice of thanksgiving. Freed therefore from our bonds, when through the Sacrament of Baptism we come unto the Sign of the Lord, we renounce the Devil and all his angels, whom before we served, that we should now serve them no longer, being delivered by the Blood and Name of Christ. But if after this any one forgetful of himself and ignorant of his redemption, return again to the serving of Angels, and to the weak and beggarly elements of the world; he shall be bound again by his old fetters and chains, that is, by the bonds of sin, and his last state shall be worse than his first. For the Devil shall bind him more strongly, as if overtaken in flight, and Christ shall not now be able to suffer for him; for, Christ being raised from the dead dieth no more. Therefore, dearly beloved, we are washed once, once are set free, are once admitted into the kingdom of heaven; once is that, blessed is he whose unrighteousness is forgiven, and whose sin is covered. Hold mightily what ye have received; keep it. blessedly, sin no more. Preserve yourselves pure and unspotted from that time even to the Day of the Lord. Great and boundless are the rewards granted unto the faithful, which eye hath not seen, nor ear heard, neither have they entered into the heart of man. These rewards that ye may receive, obtain by the labours of righteousness and spiritual vows! Amen.