John 3:3-7 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. 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? 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. That which is born of the flesh is flesh; and that which is born of the Spirit is spirit. Marvel not that I said unto thee, Ye must be born again.
Scofield’s notes on Regeneration:
(1) The necessity of the new birth grows out of the incapacity of the natural man to "see" or "enter into" the kingdom of God. However gifted, moral, or refined, the natural man is absolutely blind to spiritual truth, and impotent to enter the kingdom; for he can neither obey, understand, nor please God. John3:3, 5, 6; Ps 51:5; Jer 17:9; Mark 7:21-23; 1Co 2:14; Rom 8:7, 8; Eph 2:3 (See Note for Mat 6:33)
(2) The new birth is not a reformation of the old nature (See Note for Rom 6:6) but a creative act of the holy Spirit. John 3:5; John 1:12, 13; 2Co 5:17; Eph 2:10; Eph 4:24
(3) The condition of the new birth is faith in Christ crucified. John 3:14, 15; John 1:12, 13; Gal 3:24
(4) Through the new birth the believer becomes a partaker of the divine nature and of the life of Christ Himself. Gal 2:20; Eph 2:20; Eph 4:24; Col 1:27; 1Pe 1:23-25; 2Pe 1:4; 1Jn 5:10-12