Some key quotes that demonstrate against the idea that baptismal regeneration was unanimous by the early church fathers and early church writers.
“That baptismal washing is a sealing of faith, which faith is begun and is commended by the faith of repentance. We are not washed in order that we may cease sinning, but because we have ceased, since in heart we have been bathed already.“
Tertullian, (155-220 AD) On Repentance 6 (written around 198-200 AD, before his Montantist period)
“Cornelius was a just man, who was honored with a vision of Angels, and had set up his prayers and alms-deeds as a good memorial before God in heaven. Peter came, and the Spirit was poured out upon them that believed, and they spake with other tongues, and prophesied: and after the grace of the Spirit the Scripture saith that Peter commanded them to be baptized in the name of Jesus Christ; in order that, the soul having been born again by faith, the body also might by the water partake of the grace.
Cyril of Jerusalem (313-386 AD), Catechetical Lectures, 3:4
Notice his emphasis, “the soul having been born again by faith” – then they are baptized in water.
Peter said, “cleansing their hearts by faith” – see Acts 15:8-9
Justin Martyr, (died around 165 AD), demonstrates against infant baptism and while many argue that he taught baptismal regeneration, it seems that one could argue that he is treating water baptism as a seal of faith, since he says “they are illuminated in their understandings” and the person goes through an extensive time of discipleship, learning, praying, fasting, repentance before the actual baptism:
Chapter 61. Christian baptism (Justin Martyr, First Apology)
I will also relate the manner in which we dedicated ourselves to God when we had been made new through Christ; lest, if we omit this, we seem to be unfair in the explanation we are making. As many as are persuaded and believe that what we teach and say is true, and undertake to be able to live accordingly, are instructed to pray and to entreat God with fasting, for the remission of their sins that are past, we praying and fasting with them. Then they are brought by us where there is water, and are regenerated in the same manner in which we were ourselves regenerated. For, in the name of God, the Father and Lord of the universe, and of our Savior Jesus Christ, and of the Holy Spirit, they then receive the washing with water. For Christ also said, Unless you be born again, you shall not enter into the kingdom of heaven.
(footnote says, John 3:5, but it is actually John 3:3) Now, that it is impossible for those who have once been born to enter into their mothers’ wombs, is manifest to all. And how those who have sinned and repent shall escape their sins, is declared by Esaias the prophet, as I wrote above; he thus speaks: Wash you, make you clean; put away the evil of your doings from your souls; learn to do well; judge the fatherless, and plead for the widow: and come and let us reason together, says the Lord. And though your sins be as scarlet, I will make them white like wool; and though they be as crimson, I will make them white as snow. But if you refuse and rebel, the sword shall devour you: for the mouth of the Lord has spoken it.
Isaiah 1:16-20
And for this [rite] we have learned from the apostles this reason. Since at our birth we were born without our own knowledge or choice, by our parents coming together, and were brought up in bad habits and wicked training; in order that we may not remain the children of necessity and of ignorance, but may become the children of choice and knowledge, and may obtain in the water the remission of sins formerly committed, there is pronounced over him who chooses to be born again, and has repented of his sins, the name of God the Father and Lord of the universe; he who leads to the laver the person that is to be washed calling him by this name alone. For no one can utter the name of the ineffable God; and if any one dare to say that there is a name, he raves with a hopeless madness. And this washing is called illumination, because they who learn these things are illuminated in their understandings. And in the name of Jesus Christ, who was crucified under Pontius Pilate, and in the name of theHoly Ghost, who through the prophets foretold all things about Jesus, he who is illuminated is washed.” (My bolding emphasis) (See the ccel link to Justin Martyr, First Apology, chapter 61)
Justin’s phrase, “And this washing is called illumination, “, does seem to teach baptismal regeneration.
However, taken in the whole section, the emphasis is on the person’s learning, receiving instruction and teaching, repentance, the choice of “in which we dedicate ourselves to God”, “persuaded and believe that what we teach and say is true”, “but may become the children of choice and knowledge”,”who chooses to be born again”, and “has repented of his sins”; And this washing is called illumination, because they who learn these things are illuminated in their understandings. And in the name of Jesus Christ, who was crucified under Pontius Pilate, and in the name of the Holy Ghost, who through the prophets foretold all things about Jesus, he who is illuminated is washed.” – or “he who has been taught and repented, is then washed.” Timothy Kauffman is right when he points out that this does not say, “he who is washed is illuminated”. Rather it says the one who has been illuminated is then washed. The washing/baptizing comes after the repentance and learning and praying and fasting, as a symbol, sign, and seal of the illumination of the heart and mind. The illumination takes place in the learning, understanding, repentance, choosing to follow Christ, then the person who is illuminated (taught, learned, chosen, repented, fasted, prayed, etc.), then they are brought to the water and are washed or baptized. So it seems that Justin taught that the baptism is like a seal, a sign and symbol of the internal illumination of the mind and heart in repentance, faith, and learning about the doctrines of Christ.
For more, see my previous article on this.
Another juicy quote by Tertullian, that demonstrates against infant baptism:
And so, according to the circumstances and disposition, and even age, of each individual, the delay of baptism is preferable; principally, however, in the case of little children. For why is it necessary — if (baptism itself) is not so necessary — that the sponsors likewise should be thrust into danger? Who both themselves, by reason of mortality, may fail to fulfil their promises, and may be disappointed by the development of an evil disposition, in those for whom they stood? The Lord does indeed say, Forbid them not to come unto me. Let them come, then, while they are growing up; let them come while they are learning, while they are learning whither to come; let them become Christians when they have become able to know Christ. Why does the innocent period of life hasten to the remission of sins? More caution will be exercised in worldly matters: so that one who is not trusted with earthly substance is trusted with divine! Let them know how to ask for salvation, that you may seem (at least) to have given to him that asks. For no less cause must the unwedded also be deferred — in whom the ground of temptation is prepared, alike in such as never were wedded by means of their maturity, and in the widowed by means of their freedom — until they either marry, or else be more fully strengthened for continence. If any understand the weighty import of baptism, they will fear its reception more than its delay: sound faith is secure of salvation.
Tertullian, On Baptism, Chapter 18
Apologetics and Agape 