John 3:6

That which is born (produced), &c. Christ says this both to show the necessity of regeneration by water and the Holy Ghost, and at the same time to declare the reason for it, its excellence and its profit. His argument then is as follows: Flesh and blood cannot possess the kingdom of God, for they are carnal, but the kingdom of God is spiritual. Since therefore of carnal generation only flesh is born, that is, the animal and carnal man, bound under sin, and prone to sin, and so unfitted for the kingdom of God, it follows that if such an one would enter into God's spiritual kingdom, he must be spiritually born again of water and the Spirit, that he may become a spirit, that is, spiritual, and so fitted for the kingdom of God. Wherefore you have no cause for wonder, 0 Nicodemus, at what I said, that thou must be born again of water and the Holy Ghost. For as flesh generates flesh, that is, corporeal and carnal substance, so does the Spirit generate spirit, that is, spiritual substance: for like generates like. The Holy Spirit transmits His own substance into that which He begets, so far as it can be transmitted. For the Holy Spirit cannot transmit, or transfuse His own substance, or His Deity, into the baptized, for that would be to make them really and truly gods, as He Himself is really and truly God, which would be impossible. Therefore He transfuses Himself into them as far as is possible, by His grace and spiritual gifts, by which He makes the baptized like unto Himself, that is, spiritual, holy, heavenly, and divine. So SS. Cyril, Chrysostom, and others. Let us add that the Holy Spirit gives Himself with His sevenfold gifts to the soul which He sanctifies, and adopts for His child; and therefore that His justification is truly spiritual regeneration, by which we are born again as sons, and partakers of the Divine nature, as I have shown at large in Hosea 1:10, on the words, "Ye shall be called the sons of the living God."