John 3:6

John 3:6. That which is born of the flesh is flesh: and that which is born of the Spirit is spirit.

A man may have the best parents that ever lived, but all that is born of the flesh is flesh, at the very best. Your father may be a saint, and your mother a saint, but thou art born in sin, for that which is born of the flesh is flesh, and unless thou be born of the Spirit, thou canst not understand or see spiritual things, and thou canst not enter into the spiritual kingdom, for thou hast no spiritual capacity. "The carnal mind discerneth not the things that are of God, for they are spiritual, and must be spiritually discerned." Therefore we must be born again so as to receive that Spirit by which spiritual things are discerned and entered into.