Jesus answered, “I tell you the truth, no one can enter the kingdom of God unless he is born of water and the Spirit.
All of us are born of water. We are first raised in the water of our mothers womb, and the majority of our body is even made up of water. The Messiah did not demanded Nicodemus to climb back into his mothers womb, and be re-birthed physically. He told the Torah teacher to let the Spirit of God reveal that He was facing the Messiah, not only a miracle man. The known and respected Jewish teacher was facing the only gate to Heaven. The only Son of God who can take away our eternal punishment for sin.
The Scripture reference to being “born again” or “regenerated” is John 3:5, where 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 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 (Rom. 6:3–4; Col. 2:12–13; Titus 3:5).
No Church Father referred to John 3:5 as anything other than water baptism. Clearly, the context implies that born of “water and the Spirit” refers to baptism. The Evangelist tells us that immediately after talking with Nicodemus, Jesus took his disciples into the wilderness where they baptized people (John 3:22). Furthermore, water is closely linked to the Spirit throughout John’s Gospel (for instance, in Jesus’ encounter with the Samaritan woman at the well in John 4:9-13) and in the Johannine tradition (cf. 1 John 5:7). It seems reasonable, then, to conclude that John the Evangelist understands Jesus’ words about being “born again” and “born of water and the Spirit” to have a sacramental, baptismal meaning.