John 3:5, Jesus says, "Truly, truly, I say to you, unless one is born of water and the Spirit, he cannot enter the kingdom of God."
This verse is so important that those who say baptism is just a symbol must deny that Jesus here refers to baptism. "Born again" Christians claim that the "water" is the preached word of God.
But the early Christians uniformly identified this verse with baptism. Water baptism is the way, they said, that we are born again and receive new life—a fact that is supported elsewhere in Scripture (cf. Rom. 6:3–4; Col. 2:12–13; Titus 3:5).
No early Christian or early Church Father referred to John 3:5 as anything other than water baptism