Writing against Gnostic heretics who rejected baptismal regeneration (like many modern Evangelical anti-Mormons and others with an anti-biblical view of water baptism), Irenaeus of Lyons wrote:
It happens that their tradition respecting redemption is invisible and incomprehensible, as being the mother of things which are incomprehensible and invisible; and on this account, since it is fluctuating, it is impossible simply and all at once to make known its nature, for every one of them hands it down just as his own inclination prompts. Thus there are as many schemes of "redemption" as there are teachers of these mystical opinions. And when we come to refute them, we shall show in its fitting-place, that this class of men have been instigated by Satan to a denial of that baptism which is regeneration to God, and thus to a renunciation of the whole [Christian] faith.
They maintain that those who have attained to perfect knowledge must of necessity be regenerated into that power which is above all. For it is otherwise impossible to find admittance within the Pleroma, since this [regeneration] it is which leads them down into the depths of Bythus. For the baptism instituted by the visible Jesus was for the remission of sins, but the redemption brought in by that Christ who descended upon Him, was for perfection; and they allege that the former is animal, but the latter spiritual. And the baptism of John was proclaimed with a view to repentance, but the redemption by Jesus was brought in for the sake of perfection. And to this He refers when He says, "And I have another baptism to be baptized with, and I hasten eagerly towards it." Moreover, they affirm that the Lord added this redemption to the sons of Zebedee, when their mother asked that they might sit, the one on His right hand, and the other on His left, in His kingdom, saying, "Can ye be baptized with the baptism which I shall be baptized with?" Paul, too, they declare, has often set forth, in express terms, the redemption which is in Christ Jesus; and this was the same which is handed down by them in so varied and discordant forms. (Against Heresies 1.21.1-2 [ANF 1:345-46])
Elsewhere, he wrote:
This is why the Lord promised to send the Paraclete, who is to prepare us for God. For just as dry wheat, without water, cannot be made into a mass of dough or one loaf, so neither can we, being many, become one in Christ Jesus without the water that comes from heaven. And just as dry soil, if it does not receive water, is not fruitful, so we who were originally dry wood, could never have brought forth the fruits of life without rain graciously given from above.
By the bath [of baptism] our bodies have received the unity that renders them incorruptible; but our souls have received this by means of the Spirit. For this reason both are necessary since both obtain the life of God. Our Lord took pity on the erring Samaritan woman who, not staying with one husband, fornicated with many; he showed and promised her “the living water” so that “she would thirst no more” nor labor to obtain the refreshing water. Henceforth she has within herself the water “flowing forth unto eternal life,” the water the Lord received as a gift from his Father and which is given to those who partake of him who sends the Holy Spirit over all the earth. (Lawrence J. Johnson, Worship in the Early Church: An Anthology of Historical Sources [2 vols.; Collegeville, Minn.: Liturgical Press, 2009], 1:75)
On the overwhelming biblical evidence supporting baptismal regeneration, see, for e.g.:
John Greer vs. the biblical doctrine of baptismal regeneration
