One of the aspects of becoming a Christian is a new birth. Jesus spoke of this new birth to Nicodemus, who asked how a person can be born when he is old (John 3:4) in response to Jesus telling him that he must be born from above to see the Kingdom of God (John 3:3).
To understand what the new birth is and why it is necessary, we need to go back to the beginning. When Adam was created, He was made in the image (had a garment of light) and likeness (intelligent, rational) of God (Genesis 1:26). Even though as part of the original creation of humans God made us both male and female, He only created Adam. Therefore, Eve is not an individual creation; rather, she was built out from Adam’s side by God to be a helpmeet for him (Genesis 2:22), making it possible for the human race to propagate. Since we are all part of a single creation, Adam’s nature is passed on to his offspring. However, he did not pass on his original nature; rather, the nature his descendants receive was after he had corrupted it by trespassing and sinning (Genesis 5:3). This means that we all inherited his condemnation (Romans 5:12), and the spiritual and physical deaths that were a result of his trespass and sin (Romans 5:12-21). Physical death does not come upon us because of our personal sins, but as a direct result of Adam’s sin (Romans 5:14). Therefore, even if a human could live a completely righteous life before God, it would not be sufficient to save that one because the head of our creation is corrupt, condemned, and separated from God and therefore all his offspring are also in this state (Romans 3:23).
This is why God had to create a new man to be the head. As a single creation, the human race cannot be without a head. In resurrecting Christ, God created a new man in which Christ is the head and the Church is His body (Ephesians 1:22,23; Since someone is in Christ, a new creation … 2 Corinthians 5:17). We do not become a new creation, or as some translations imply, a new creature; rather, the Christ is a new creation in which we are placed.
All those in Adam are a result of propagation; however, all those in Christ are a result of immersion. The Holy Spirit immerses believers into the body of the Christ, taking them out of Adam and placing them into Christ (1 Corinthians 12:12-13). In order to do this, the Holy Spirit has to wash and regenerate us, which cleanses from sins and places God seed within us so that we become legitimate children of God (1 John 3:2,9). This is the new birth. We are now, literally, born from above, just as Jesus said was required to see the Kingdom of God.
not out from works, the ones in righteousness, which we have done, but according to His mercy He saved us through washing of regeneration and renewing from the Holy Spirit – Titus 3:5.
Our new birth is not a birth from a corrupt seed; rather, we are born again from an incorruptible seed (1 Peter 1:23). Therefore, as ones who are born again, we are no longer condemned in Adam (Romans 8:1) but are now righteous in Christ (1 Corinthians 1:30). Although we have not yet received our full redemption, for that will be at the saving of our souls (1 Peter 1:9), which is the last part of us to be saved when we are resurrected and see Christ (1 John 3:2), God imputes Christ’s righteousness to us now and therefore gives us all things pertaining to life and godliness (2 Peter 1:3-4) through which we escape the corruption of this world through its desires.