“You Shall Open Your Mouth to Declare My Gospel”
Doctrine and Covenants 30:5–8
5 Behold, I say unto you, Peter, that you shall take your journey with your brother Oliver; for the time has come that it is expedient in me that you shall open your mouth to declare my gospel; therefore, fear not, but give heed unto the words and advice of your brother, which he shall give you.
6 And be you afflicted in all his afflictions, ever lifting up your heart unto me in prayer and faith, for his and your deliverance; for I have given unto him power to build up my church among the Lamanites;
7 And none have I appointed to be his counselor over him in the church, concerning church matters, except it is his brother, Joseph Smith, Jun.
8 Wherefore, give heed unto these things and be diligent in keeping my commandments, and you shall be blessed unto eternal life. Amen.
President Joseph Fielding Smith wrote:
“To Peter Whitmer Jr. the Lord gave a commandment that he should take his journey with Oliver Cowdery on a mission to the Lamanites. From the very beginning the attention of the Prophet and his brethren had been drawn to the Lamanites. This was due, of course, to the fact that great promises had been made to them in the Book of Mormon that the gospel would be given to them in this dispensation and eventually they would be restored to full fellowship and favor before the Lord. The enthusiasm of the brethren may have been premature, but nevertheless the Lord commanded such a mission at that time. It seems that it was not so much for the benefit of the Indians, or Lamanites, although that factor was very great, but to carry the message to the land which later was to be revealed as the land of Zion, where the City Zion will eventually be built. Peter Whitmer Jr. was also one of the Eight Witnesses of the Book of Mormon.
“Peter was informed that he was to heed the words of his brother, Oliver Cowdery, and he was to share with him in all his afflictions, lifting his heart to the Lord in prayer and faith, for their deliverance. ‘I have given unto him power to build up my church among the Lamanites’ [D&C 30:6]. Moreover, Peter was informed that there was none appointed to be Oliver’s counselor, except Joseph Smith. Thus Peter understood that it was his duty to take, not to give, counsel while on this journey. The fact that Oliver Cowdery had shared with Joseph Smith in the conferring of priesthood and authority on all occasions naturally gave to him the authority to stand second in the Church to Joseph Smith in the government of the Church.”
(Church History and Modern Revelation, 2 vols. , 1:146–47.)