“The Same Yesterday, Today, and Forever”

Joseph F. McConkie, Robert L. Millet
The whole system of salvation depends upon the constancy of God. Were it not for the knowledge that God’s perfection is not of recent origin or something which he must yet obtain, we could hardly be expected to value that which he spoke anciently or not wonder about the possibility of his changing his mind about that which he asks of us at present. (See also Mormon 9:19; Moroni 8:18; D&C 20:12, 17.)

Doctrinal Commentary on the Book of Mormon, Vol. 1