John 3:5-6 - Flesh gives birth to flesh, but the Spirit gives birth to spirit

Jesus answered, "I tell you the truth, no one can enter the kingdom of God unless he is born of water and the Spirit. Flesh gives birth to flesh, but the Spirit gives birth to spirit.

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.

Jesus answered, "Truly, truly, I say to you, unless one is born of water and 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.

John 3:5-6

Commentary

Physical birth is not enough. There must also be a spiritual birth if one is to enter the kingdom of God. This spiritual birth is produced by the Holy Spirit of God when a person believes on the Lord Jesus Christ. This interpretation is supported by the fact that the expression "born of the Spirit" is found twice in the verses to follow (vv. 6, 8). 

MacDonald, W., & Farstad, A. (1997, c1995). Believer's Bible Commentary : Old and New Testaments (Jn 3:5). Nashville: Thomas Nelson.