That which is born of the flesh is flesh. — The first step is to remind him of the law of likeness in natural generation. “Flesh,” as distinct from “spirit,” is human nature in so far as it is common with animal nature, consisting of the bodily frame and its animal life, feelings, and passions. “Flesh,” as opposed to “spirit,” is this nature as not under the guidance of the human spirit, which is itself the shrine of the Divine Spirit, and therefore it is sinful. (Comp. Galatians 5:16 et seq.; Galatians 6:8.) It is this nature in its material constitution, and subject to sin, which is transmitted from father to son. The physical life itself is dependent upon birth. That which is born of the flesh is flesh.
There is an analogous law of spiritual generation. Spirit as opposed to flesh is the differentia of man as distinct from all other creatures. It is the image of God in him, the seat of the capacity for the communion with God, which is the true principle of life. In the natural man this is crushed and dormant; in the spiritual man it has been quickened by the influence of the Holy Ghost. This is a new life in him, and the spiritual life, like the physical, is dependent upon birth. That which is born of the Spirit is spirit.
(6) The sense suggested for the last clause, “In this manner is every one born who is of the Spirit,” removes the necessity of finding something with which the work of the Spirit may be compared, and it is in this necessity that the received versions of the first clause really find their root.
These reasons are, it is thought, not an insufficient basis for the interpretation here adopted. It is adopted not without the knowledge that a consensus of authorities may be pleaded against it. For its details it may be that no authority can be pleaded, but the rendering of πνεῦμα here by “spirit” is not without the support of width of learning and depth of power, critical acumen and spiritual insight, for it rests on the names of Origen and Augustine, of Albrecht Bengel and Frederick Maurice.