Isaiah 59:21

As for Me, this is My covenant with them, saith the Lord, this explains why He had not rejected the entire nation outright: My Spirit that is upon thee, upon Israel, especially in its representative leaders and prophets, and My words which I have put in thy mouth, shall not depart out of thy mouth, the Word of salvation remaining with His Church forever, nor out of the mouth of thy seed, the spiritual seed of Israel, nor out of the mouth of thy seed's seed, saith the Lord, from henceforth and forever. The Lord kept His covenant faithfulness to the end, the entire history of the Church, both before and after the coming of the Messiah being proof of that fact. His mercy includes not only all the true descendants of the patriarchs in Israel, but embraces heathen from every nation in the world as well.