That which is born of the flesh is flesh. That which is born of the Spirit is spirit.
Here another question arises; for it is certain that in this degenerate and corrupted nature some remnant of the gifts of God still lingers; and hence it follows that we are not in every respect corrupted. The reply is easy. The gifts which God hath left to us since the fall, if they are judged by themselves, are indeed worthy of praise; but as the contagion of wickedness is spread through every part, there will be found in us nothing that is pure and free from every defilement. That we naturally possess some knowledge of God, that some distinction between good and evil is engraven on our conscience, that our faculties are sufficient for the maintenance of the present life, that — in short — we are in so many ways superior to the brute beasts, that is excellent in itself, so far as it proceeds from God; but in us all these things are completely polluted, in the same manner as the wine which has been wholly infected and corrupted by the offensive taste of the vessel loses the pleasantness of its good flavor, and acquires a bitter and pernicious taste. For such knowledge of God as now remains in men is nothing else than a frightful source of idolatry and of all superstitions; the judgment exercised in choosing and distinguishing things is partly blind and foolish, partly imperfect and confused; all the industry that we possess flows into vanity and trifles; and the will itself, with furious impetuosity, rushes headlong to what is evil. Thus in the whole of our nature there remains not a drop of uprightness. Hence it is evident that we must be formed by the second birth, that we may be fitted for the kingdom of God; and the meaning of Christ’s words is, that as a man is born only carnal from the womb of his mother; he must be formed anew by the Spirit, that he may begin to be spiritual. 