Jesus answered, “ Most assuredly, I say to you, unless one is born of water and the Spirit, he cannot enter the kingdom of God. – John 3:5
Just like a natural man is born of a mother and a father, so the spiritual man must be born of water (the Word – James 1:18, 1 Pet 1:23, Eph 5:26) and the Spirit. Just like a natural man owes his existence to the influences of both his father and his mother, and requires them both to be born, so must the spiritual man be of the influence of both the Word of God and of the Holy Spirit. The Word is what we must believe to be saved (for how can we believe if we do not hear? – Rom 10:14), and the Spirit must press us to believe that word, for no man comes to the Father except the Spirit draw him.
When a man receives the Word of God, pressed by the Spirit of God, he must allow God to make a complete change in his heart and mind. His life is no longer the same. The purpose of his existence no longer is himself, but the will of God. His whole outlook is different. The Spirit of God comes to live on the inside of him, empowering him to live a holy life.
What literally happens to a man when he is born again? The Holy Spirit comes to live in him. His heart’s desire becomes to serve God. The Spirit now will work in him to will and to do of His good pleasure.