In the third chapter of John, a Pharisee named Nicodemus went to Jesus and said he believed that no one could do the miracles he did unless God was with him and Jesus immediately engaged him in a dialogue about how one must be born again.
"Verily, verily, I say unto thee, Except a man be born again, he cannot see the kingdom of God."
"...How can a man be born when he is old? can he enter the second time into his mother's womb, and be born?"
"...Except a man be born of water and of the Spirit, he cannot enter into the kingdom of God. That which is born of the flesh is flesh; and that which is born of the Spirit is spirit."
Apparently Nicodemus didn't get it because Jesus said to him in the very next verse, "Marvel not that I said unto thee, Ye must be born again. The wind bloweth where it listeth, and thou hearest the sound thereof, but canst not tell whence it cometh, and whither it goeth: so is every one that is born of the Spirit." (John 3:4-8)
The word used for "born again" is the same word as "above." Therefore, being born again is a new birth from above- a spiritual birth or regeneration.
In essence, what Jesus is telling Nicodemus is that he must be born from above through the power of the Holy Spirit. When we are born into this world we are mere flesh, but through faith in the Son of God we are born again spiritually. "For God so loved the world, that he gave his only begotten Son, that whosoever believeth in him should not perish, but have everlasting life." (John 3:16) Paul enforced this by saying, "Flesh and blood shall not inherit the Kingdom of God."
In order to be born again (saved) a person must hear and believe the truth of the gospel. To believe is to have faith and faith comes by the word of God. In other words, no human words have the power to regenerate. The power of the word of God penetrates to the very core of our being and we become a living soul. "So then faith cometh by hearing, and hearing by the word of God." (Romans 10:17) It is the power of God and not of us.
When we are born again, the spirit within is but a child. The scriptures and the Holy Spirit nurtures our spirit as it begins to grow and mature. "As newborn babes, desire the sincere milk of the word, that ye may grow thereby." (2Peter 1:2)
Salvation is a gift of God but so many try desperately to earn it. Paul stated quite emphatically, "For by grace are ye saved through faith; and that not of yourselves: it is the gift of God: Not of works, lest any man should boast." (Eph. 28-9)
However, when one is born again, works will eventually follow as the spirit matures. One is not saved by works but works are the ultimate results of salvation.
James, the brother of our Lord, touched on this when he said, "Even so faith, if it hath not works, is dead, being alone. Yea, a man may say, Thou hast faith, and I have works: shew me thy faith without thy works, and I will shew thee my faith BY my works." (James 2:17)
Being born again is a spiritual birth without which we cannot enter heaven. "Flesh and blood cannot inherit the kingdom of God." (1Cor.15:5)
For this reason, since no one is guaranteed another day of life here on this earth, it is imperative that we be born again. Otherwise, when we die our body returns to the dust from whence it came and the spirit goes back to God who gave it. (Ecc. 12:7)
In order to be born again we must recognize the sin in our lives contrast to the holiness of God which is the absolute absence of sin. When we are born again, we are clothed with the righteousness of Christ which gives us direct access to the throne of God.