This statement concerning the unchangeable nature of God occurs several times in the Book of Mormon (see also 2 Nephi 2:4; Alma 31:17; Mormon 9:9; and Moroni 10:19). It occurs also in the Lord’s own testimony about the divinity of His word as contained in the Book of Mormon:
Proving to the world that the holy scriptures are true, and that God does inspire men and call them to his holy work in this age and generation, as well as in generations of old;
Thereby showing that he is the same God yesterday, today, and forever. Amen” (D&C 20:11–12).
The Supreme Being exists as the “Unchanging One,” or Jehovah, for that is the meaning of this name.