The difference between Jews and Gentiles, which was so important to the Jews of Christ’s day, is abolished with the gospel of Jesus Christ, there is neither Jew nor Greek…for ye are all one in Christ Jesus. And if ye be Christ’s, then are ye Abraham’s seed, and heirs according to the promise (Gal 3:28-9). Those Gentiles who repent and receive Christ as their Savior will become the covenant people of the Lord. They are effectively adopted into the house of Israel. Conversely, those Jews who reject Christ will be cast off as though no promises were ever made to them.
The significance of being adopted into the house of Israel begins with the promises made to Abraham. Because of Abraham’s great faith and obedience, even that he would offer his son Isaac, the Lord promised him, That in blessing I will bless thee, and in multiplying I will multiply thy seed as the stars of the heaven, and as the sand which is upon the sea shore; and thy seed shall possess the gate of his enemies; And in thy seed shall all the nations of the earth be blessed (Gen 22:17-8). Those who understand the true meaning of the promise of eternal life and eternal increase understand that seed multiplied as the stars of the heaven is an eternal and not merely a mortal promise. Thy seed shall possess the gate of his enemies, means that the Lord will bless them, prosper them, and protect them from political oppression. In thy seed shall all the nations of the earth be blessed is fulfilled in several respects. First, the house of Israel will do the genealogy and temple work for the dead and perform temple ordinances for the returning ten tribes, becoming saviors on mount Zion, And there shall they (the 10 tribes) fall down and be crowned with glory, even in Zion, by the hands of the servants of the Lord, even the children of Ephraim (DC 133:32). Second, the Savior of the world and most of the prophets were to come through the lineage of Israel. Third, the gospel will be brought to the world primarily through the house of Israel. Fourth, the world has been blessed by the contributions to art, science, inventions, industry, philosophy, politics, etc. made by the descendants of Abraham.
Other promises related to the covenant made with Abraham are to be had in the temple of God. John the Revelator explained that those who are sanctified by Jesus Christ are made kings and priests unto God (Rev 1:6). This phrase could be rendered kings and priests in the house of Israel for it is through the house of Israel that the Lord establishes his church and reigns in his kingdom, for now and for all time. All of these promises that are part of the Abrahamic covenant are available to every member of the church. They are promises with incredible eternal consequence which are often under appreciated.
Joseph Smith taught that there was an actual spiritual transformation which purges out the old blood, “the effect of the Holy Ghost upon a Gentile, is to purge out the old blood, and make him actually of the seed of Abraham. That man that has none of the blood of Abraham (naturally) must have a new creation by the Holy Ghost.” (Teachings of the Prophet Joseph Smith, p. 150) See also Rom 9:6-8, DC 103:17, and the Bible Dictionary on “Adoption.”