4 “Alienated are sinners from the womb, they have gone astray from the belly, they have spoken false things”. And when iniquity they speak, false things they speak; because deceitful is iniquity: and when justice they speak, false things they speak; because one thing with mouth they profess, another thing in heart they conceal. “Alienated are sinners from the womb.” What is this? Let us search more diligently: for perhaps he is saying this, because God has foreknown men that are to be sinners even in the wombs of their mothers. For whence when Rebecca was yet pregnant, and in womb was bearing twins, was it said, “Jacob I have loved, but Esau I have hated”? For it was said, “The elder shall serve the younger.”
Hidden at that time was the judgment of God: but yet from the womb, that is, from the very origin, alienated are sinners. Whence alienated? From truth. Whence alienated? From the blessed country, from the blessed life. Perchance alienated they are from the very womb. And what sinners have been alienated from the womb? For what men would have been born, if therein they had not been held? Or what men today would be alive to hear these words to no purpose, unless they were born? Perchance therefore sinners have been alienated from a certain womb, wherein that charity was suffering pains, which speaks through the Apostle, “Of whom again I am in labour, until Christ be formed in you.” Expect thou therefore; be formed: do not to yourself ascribe a judgment which perchance you know not.
Carnal you are as yet, conceived you have been: from that very time when you have received the name of Christ, by a sort of sacrament you have been born in the bowels of a mother. For not only out of bowels a man is born, but also in bowels. First he is born in bowels, in order that he may be able to be born of bowels. Wherefore it has been said even to Mary, “For that which is born in you, is of the Holy Spirit.” Not yet of Her It had been born, but already in Her It had been born.
Therefore there are born within the bowels of the Church certain little ones, and a good thing it is that being formed they should go forth, so that they drop not by miscarriage. Let the mother bear you, not miscarry. If patient you shall have been, even until you be formed, even until in you there be the sure doctrine of truth, the maternal bowels ought to keep you. But if by your impatience you shall have shaken the sides of your mother, with pain indeed she expels you out, but more to your loss than to hers.
Source: The Enarrations, or Expositions, on the Psalms (New Advent)