Mormon urges the Gentiles to repent.

3 Nephi 30:1–2

1 Hearken, O ye Gentiles, and hear the words of Jesus Christ, the Son of the living God, which he hath commanded me that I should speak concerning you, for, behold he commandeth me that I should write, saying:
2 Turn, all ye Gentiles, from your wicked ways; and repent of your evil doings, of your lyings and deceivings, and of your whoredoms, and of your secret abominations, and your idolatries, and of your murders, and your priestcrafts, and your envyings, and your strifes, and from all your wickedness and abominations, and come unto me, and be baptized in my name, that ye may receive a remission of your sins, and be filled with the Holy Ghost, that ye may be numbered with my people who are of the house of Israel.

Elder Bruce R. McConkie wrote:

“By the law of adoption those who receive the gospel and obey its laws, no matter what their literal blood lineage may have been, are adopted into the lineage of Abraham (Abraham 2:9–11). . . . Indeed, the faithful are adopted into the family of Christ; they become ‘the children of Christ, his sons, and his daughters’; they are ‘spiritually begotten,’ for their ‘hearts are changed through faith on his name,’ thus being ‘born of him,’ becoming ‘his sons and his daughters’ (Mosiah 5:7).”

(Mormon Doctrine, 2nd ed. [1966], 23.)