Jesus told Nicodemus that unless one is born again he cannot see the kingdom of God, and unless one is born of water and the Spirit he cannot enter it. Regeneration is necessary because of the miserable condition of sinful man: dead in trespasses and sins, by nature a child of wrath, hostile to God and unwilling to come to Christ. But God, rich in mercy, made us alive together with Christ, and the Spirit quickens us to walk in newness of life.
The second part calls regeneration monergistic: it is God’s work alone. What is born of the flesh is flesh, no one can bring a clean thing out of an unclean, and the Spirit blows where He wishes. Regeneration is the Holy Spirit bringing the dead sinner to life by God’s sovereign act, the washing of regeneration and the new heart promised through Ezekiel. Born again to a living hope, believers are to lay aside the old self and put on the new.