Jesus told him he must be born again in order to enter the Kingdom of God. Nicodemus not understanding asked how could he enter a second time into his mother's womb. Not realizing Jesus was talking about a spiritual birth not a natural one. Regeneration is not Baptism. In this scripture we see the importance of belief and baptism, but only unbelief condemns.
Baptism is an outward show of the new birth that has taken place on the inside.
It of itself is not the new birth. Regeneration is not reformation . It is not enough for us to clean up our act by not doing those things we think are negative and then to start doing the positive. All our righteousness are as filthy rags. It takes more than what we can do for ourselves.