2 Nephi 9
What a blessing it is to have an account of the mission of our Lord and Savior declared in the Book of Mormon to add a second witness to the doctrine declared in the Bible. Why is it important for the world to have both the Bible and the Book of Mormon? I believe the answer is found in the 13th chapter of 1 Nephi. Nephi records: “And the angel spake unto me, saying: These last records, which thou hast seen among the Gentiles [that is, the Book of Mormon], shall establish the truth of the first [which is the Bible], which are of the twelve apostles of the Lamb, and shall make known the plain and precious things which have been taken away from them; and shall make known to all kindreds, tongues, and people, that the Lamb of God is the Son of the Eternal Father, and the Savior of the world; and that all men must come unto him, or they cannot be saved” (1 Nephi 13:40).
Neither the Bible nor the Book of Mormon in and of themselves is sufficient. Both are necessary for us to teach and learn about the complete doctrine of Christ. The need for the other does not diminish either one of them. Both the Bible and the Book of Mormon are necessary for our salvation and exaltation. (“The Power of Deliverance“, Ensign, May 2012)