4 But as arising out of this occasion, this must not be passed over, which may haply of itself perplex some of you; with what design is it, that when this Jacob's grandfather Abraham's name was changed (for he too was first called Abram, and God changed his name, and said, “You shall not be called Abram, but Abraham”); from that time he was not called Abram. Search in the Scriptures, and you will see that before he received another name, he was called only Abram; after he received it, he was called only Abraham.
But this Jacob, when he received another name, heard the same words, “You shall not be called Jacob, but Israel shall you be called.” Search the Scriptures, and see how that he was always called both, both Jacob and Israel. Abram after he had received another name, was called only Abraham. Jacob after he had received another name, was called both Jacob and Israel. The name of Abraham was to be developed in this world; for here he was made the father of many nations, whence he received his name.
But the name of Israel relates to another world, where we shall see God. Therefore the people of God, the Christian people in this present time, is both Jacob and Israel, Jacob in fact, Israel in hope. For the younger people is called the Supplanter of its brother the elder people. What! Have we supplanted the Jews? No, but we are said to be their supplanters, for that for our sakes they were supplanted. If they had not been blinded, Christ would not have been crucified; His precious Blood would not have been shed; if that Blood had not been shed, the world would not have been redeemed. Because then their blindness has profited us, therefore has the elder brother been supplanted by the younger, and the younger is called the Supplanter. But how long shall this be?
Source: Sermons on Selected Lessons of the New Testament (New Advent)