The believer in Jesus Christ becomes a new creature!
2 Corinthians 5:17
Therefore if any man be in Christ, he is a new creature: old things are passed away; behold, all things are become new.
“If any man be in Christ”
When a person believes in the gospel of Jesus Christ for salvation, many wonderful spiritual things happen to him in an instant, most without his knowledge (see this link). One thing that happens is that he is fully immersed (baptized) into Jesus Christ by the Spirit of God, this is the baptism of the Holy Ghost (Mark 1:8; Acts1:5) and is not to be confused with water baptism, every Christian experiences this baptism the moment they trust Jesus Christ as their Saviour:
Romans 6:3-4
Know ye not, that so many of us as were baptized into Jesus Christ were baptized into his death? [4] Therefore we are buried with him by baptism into death: that like as Christ was raised up from the dead by the glory of the Father, even so we also should walk in newness of life.
Galatians 3:26-28
For ye are all the children of God by faith in Christ Jesus. [27] For as many of you as have been baptized into Christ have put on Christ. [28] There is neither Jew nor Greek, there is neither bond nor free, there is neither male nor female: for ye are all one in Christ Jesus.
“He is a new creature”
At the same time the new believer is baptized into Christ by the Spirit of God, he is also born again through the same Spirit. Jesus said that a man must be “born again” to see and enter into the kingdom of God, and this rebirth is being “born of the Spirit”:
John 3:3-8
Jesus answered and said unto him, Verily, verily, I say unto thee, Except a man be born again, he cannot see the kingdom of God. [4] Nicodemus saith unto him, How can a man be born when he is old? can he enter the second time into his mother’s womb, and be born? [5] Jesus answered, Verily, verily, I say unto thee, Except a man be born of water and of the Spirit, he cannot enter into the kingdom of God. [6] That which is born of the flesh is flesh; and that which is born of the Spirit is spirit. [7] Marvel not that I said unto thee, Ye must be born again. [8] 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.
The word of God also plays a part in this rebirth:
1 Peter 1:22-23
Seeing ye have purified your souls in obeying the truth through the Spirit unto unfeigned love of the brethren, see that ye love one another with a pure heart fervently: [23] Being born again, not of corruptible seed, but of incorruptible, by the word of God, which liveth and abideth for ever.
The new birth results in a new creature, and “old things are passed away; behold, all things are become new.” Just like the first birth when you were born as a baby, being born again starts in the same way, you are a baby in Christ and must grow up and mature, you start with very little knowledge and understanding about the new spiritual man you have become:
1 Peter 2:2
As newborn babes, desire the sincere milk of the word, that ye may grow thereby:
1 Corinthians 3:1-2
And I, brethren, could not speak unto you as unto spiritual, but as unto carnal, even as unto babes in Christ. [2] I have fed you with milk, and not with meat: for hitherto ye were not able to bear it , neither yet now are ye able.
Hebrews 5:13-14
For every one that useth milk is unskilful in the word of righteousness: for he is a babe. [14] But strong meat belongeth to them that are of full age, even those who by reason of use have their senses exercised to discern both good and evil.
The new creature is a new man, and he needs to grow up from being an infant into a mature Christian, learning how to daily put on the new man (spiritual) and put off the old man (carnal/flesh):
Ephesians 4:24
And that ye put on the new man, which after God is created in righteousness and true holiness.
Colossians 3:9-11
Lie not one to another, seeing that ye have put off the old man with his deeds; [10] And have put on the new man , which is renewed in knowledge after the image of him that created him: [11] Where there is neither Greek nor Jew, circumcision nor uncircumcision, Barbarian, Scythian, bond nor free: but Christ is all, and in all.
Galatians 6:15
For in Christ Jesus neither circumcision availeth any thing, nor uncircumcision, but a new creature.
