19 That holy man and eloquent bishop Augustine not long ago wrote to Marcellinus (the same that was afterwards, though innocent, put to death by heretics on the pretext of his taking part in the tyranny of Heraclian) two treatises on infant baptism, in opposition to your heresy which maintains that infants are baptized not for remission of sins, but for admission to the kingdom of heaven, according as it is written in the Gospel, “Unless a man be born again of water and of the Spirit, he cannot enter into the kingdom of heaven.”
He addressed a third, moreover, to the same Marcellinus, against those who say as do you, that a man can be free from sin, if he chooses, without the help of God. And, recently, a fourth to Hilary against this doctrine of yours, which is full of perversity. And he is said to have others on the anvil with special regard to you, which have not yet come to hand. Wherefore, I think I must abandon my task, for fear Horace's words may be thrown at me, “Don't carry firewood into a forest.”
For we must either say the same as he does, and that would be superfluous; or, if we wished to say something fresh, we should find our best points anticipated by that splendid genius. One thing I will say and so end my discourse, that you ought either to give us a new creed, so that, after baptizing children into the name of the Father, Son, and Holy Spirit, you may baptize them into the kingdom of heaven; or, if you have one baptism both for infants and for persons of mature age, it follows that infants also should be baptized for the remission of sins after the likeness of the transgression of Adam.
But if you think the remission of another's sins implies injustice, and that he has no need of it who could not sin, cross over to Origen, your special favourite, who says that ancient offenses committed long before in the heavens are loosed in baptism. You will then be not only led by his authority in other matters, but will be following his error in this also.
Source: Against the Pelagians (New Advent)