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And for this 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." (Justin Martyr, "First Apology," Ante-Nicene Fathers, vol. 1, pg. 183)

"Those who are convinced that what we teach is true and who desire to live accordingly are instructed to fast and to pray to God for the remission of all their past sins. We also pray and fast with them. Then we bring them to a place where there is water, and they are regenerated in the same manner in which we ourselves were regenerated. They then receive the washing with water in the name of God (the Father and Lord of the universe) and of our Savior Jesus Christ, and of the Holy Spirit. For Christ said, 'Unless you are born again, you shall not enter into the kingdom of heaven"' [John 3:5]. (Justin First Apology chant 61)

"Baptism itself is a corporal act by which we are plunged into the water, while its effect is spiritual, in that we are freed from our sins" (Tertullian, "On Baptism," Ante-Nicene Fathers)

“When we are going to enter the water, but a little before, in the presence of the congregation and under the hand of the president, we solemnly profess that we disown the devil, and his pomp, and his angels. Hereupon we are thrice immersed.” (Tertullian, "On Baptism," Ante-Nicene Fathers)

I'll get to Irenaeus is a bit, I need to get my sources (it's been awhile since I've been down this road, I know there's a lot in Against Heresies, I just don't remember where off the top of my head), but I'm in a hurry. Sorry.