Malachi 1:2

Who are these that reply to God, who speaks to Rebecca? She had twin sons of one conception of Isaac our father. "The children were not yet born nor had done any good or evil (that the purpose of God according to election might stand)." The election was of grace, not of merit. It is the election by which he does not find but makes elect—"that it was not of works but of him that calls, that the elder should serve the younger." To this sentence the blessed apostle adds the testimony of a prophet who came along afterward: "Jacob I have loved, but Esau I have hated" to give us to understand plainly by the later utterance what was hidden in the predestination of God by grace before they were born. For what did he love but the free gift of his mercy in Jacob, who had done nothing good before his birth? And what did he hate but original sin in Esau, who had done nothing evil before his birth? Surely he would not have loved in the former a goodness which he had not practiced, nor would he have hated in the latter a nature which he himself had created good.

At the very beginning of the world, of those two sons who were born of Adam, Abel the younger is chosen, while as a figure of the unfaithful Jews, Cain the older one is condemned. Afterward, in the time of Abraham, the same figure is fulfilled in Sarah and Hagar. Sarah was sterile for a long time as a type of the church, while Hagar as a figure of the synagogue bore a son at once. Hence it is that the younger son Isaac is received into the inheritance, but Ishmael, who was older, is driven away. This fact also seems to have been fulfilled in those two: Jacob the younger was loved by God, while Esau was rejected according to what is written: "I have loved Jacob but hated Esau." This figure is also known to have been fulfilled in those two sisters whom blessed Jacob had as his wives: Rachel, who was the younger, was loved more than Leah the older. In fact, of the former was born Joseph, who was to be sold in Egypt as a type of our Lord and Savior. That Leah was bleary-eyed while Rachel was beautiful in countenance is also significant: in Leah is understood the synagogue; the church is indicated in Rachel. A man whose bodily eyes are afflicted with inflammation cannot look at the brightness of the sun. Similarly the synagogue, which had had the eyes of its heart filled with jealousy and envy against our Lord and Savior as with poisonous floods, could not gaze upon the splendor of Christ, who is "the Sun of justice."