Who was the Messiah promised to come through in the Abrahamic covenant?

Les explains that there is a constant promise according to the Abrahamic covenants that through Abraham, Isaac, Jacob, and the twelve sons would come the Messiah. He stresses that it was not through Ishmael but through Isaac; the singular seed would come through Isaac. Les notes the Muslim world argues the Old Testament has been polluted and distorted, claiming Ishmael was the promised seed, but because the Bible is the Word of God, we can rest on it that it was through Isaac that the singular seed would come. Returning to Galatians chapter 3 and verse 16, Les says the promises were made to Abraham and his seed, the singular seed Isaac—not the whole nation, but the one man Isaac where the promises and covenant rest. Then the verse says not seeds as many but one seed, and that seed is Christ. Thus everyone, regardless of where they are in human history, benefits from this Abrahamic covenant through whom all the world would be blessed.