Ezk 36:25-27, Jn 1:12, Gal 6:15, Titus 3:5, 1 Jn 5:1, Mk 16:16, Acts 5:30-32, Acts 2:38
Jesus said that only those who are born of the Holy Spirit can enter the kingdom of God. (Jn 3:3,5)
Jn 3:3 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. 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.
In the Old Testament, it was prophesied that God would send the Holy Spirit to us. (Ezk 36:25-27)
Ezk 36:25 Then will I sprinkle clean water upon you, and ye shall be clean: from all your filthiness, and from all your idols, will I cleanse you. 26 A new heart also will I give you, and a new spirit will I put within you: and I will take away the stony heart out of your flesh, and I will give you an heart of flesh. 27 And I will put my spirit within you, and cause you to walk in my statutes, and ye shall keep my judgments, and do them.
The Holy Spirit came upon those who believed in Jesus as the Christ. Only those who believe in Jesus as the Christ become children of God. (Acts 5:30-32, Acts 2:38, Jn 1:12, 1 Jn 5:1)
Acts 5:30 The God of our fathers raised up Jesus, whom ye slew and hanged on a tree. 31 Him hath God exalted with his right hand to be a Prince and a Saviour, for to give repentance to Israel, and forgiveness of sins. 32 And we are his witnesses of these things; and so is also the Holy Ghost, whom God hath given to them that obey him.
Acts 2:38 Then Peter said unto them, Repent, and be baptized every one of you in the name of Jesus Christ for the remission of sins, and ye shall receive the gift of the Holy Ghost.
Jn 1:12 But as many as received him, to them gave he power to become the sons of God, even to them that believe on his name:
1 Jn 5:1 Whosoever believeth that Jesus is the Christ is born of God: and every one that loveth him that begat loveth him also that is begotten of him.
We can be born again only by the Holy Spirit, which is given through faith in Jesus as the Christ, neither by circumcision nor by uncircumcision nor by works of righteousness. (Gal 6:15, Titus 3:5)
Gal 6:15 For in Christ Jesus neither circumcision availeth any thing, nor uncircumcision, but a new creature.
Titus 3:5 Not by works of righteousness which we have done, but according to his mercy he saved us, by the washing of regeneration, and renewing of the Holy Ghost;