25 But the same mother which brought forth Abel, and Enoch, and Noah, and Abraham, brought forth also Moses and the prophets who succeeded him till the coming of our Lord; and the mother which gave birth to them gave birth also to our apostles and martyrs, and all good Christians. For all these that have appeared have been born indeed at different times, but are included in the society of our people; and it is as citizens of the same state that they have experienced the labors of this pilgrimage, and some of them are experiencing them, and others will experience them even to the end.
Again, the mother who brought forth Cain, and Ham, and Ishmael, and Esau, brought forth also Dathan and others like him in the same people; and she who gave birth to them gave birth also to Judas the false apostle, and Simon Magus, and all the other false Christians who up to this time have persisted obstinately in their carnal affections, whether they have been mingled in the unity of the Church, or separated from it in open schism. But when men of this kind have the gospel preached to them, and receive the sacraments at the hand of those who are spiritual, it is as though Rebecca gave birth to them of her own womb, as she did to Esau; but when they are produced in the midst of the people of God through the instrumentality of those who preach the gospel not sincerely, Sarah is indeed the mother, but through Hagar.
So when good spiritual disciples are produced by the preaching or baptism of those who are carnal, Leah, indeed, or Rachel, gives birth to them in her right as wife, but from the womb of a handmaid. But when good and faithful disciples are born of those who are spiritual in the gospel, and either attain to the development of spiritual age, or do not cease to strive in that direction, or are only deterred from doing so by want of power, these are born like Isaac from the womb of Sarah, or Jacob from the womb of Rebecca, in the new life and the new covenant.
Source: On Baptism, Against the Donatists (New Advent)