The First Extra-Biblical Account Of Baptism

I will also relate the manner in which we dedicate ourselves to God when we have been made new through Christ… Those who believe that what we teach and say is true, and undertake 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. In the name of God, the Father and Lord of the universe, and of our Saviour Jesus Christ, and of the Holy Spirit, they are then washed with water.

For Christ said, "Unless you be born again, you shall not enter into the kingdom of heaven." Now, it is manifest to all that is impossible for those who have once been born to enter into their mothers' wombs. And how those who have sinned and repent shall escape their sins, is declared by Isaiah the prophet: "Wash yourselves clean; put away your misdeeds from your souls; learn to do good… Come now, let us set things right, says the Lord. And though your sins be like scarlet, I will make them white like wool." (Is 1:16 f)… This is what we have learned from the apostles. At our birth we were born without our own knowledge or choice, by our parents coming together… 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 water the remission of sins formerly committed, we pronounce over those who choose to be born again, and have repented of their sins, the name of God the Father and Lord of the universe; he who leads to baptism the person that is to be washed calls God by this name alone. For no one can utter the name of the ineffable God...

And this washing is called illumination, because they who learn these things are illuminated in their understanding. And he who is illuminated is washed in the name of Jesus Christ, who was crucified under Pontius Pilate, and in the name of the Holy Spirit, who through the prophets foretold all things about Jesus.

-St. Justin Martyr (d. 160 AD)