“An ‘apostle’ is an ordained leader in the Melchizedek Priesthood in The Church of Jesus Christ of Latter-day Saints. Apostles are chosen through inspiration by the President of the Church, sustained by the general membership of the Church, and ordained by the First Presidency and Quorum of the Twelve Apostles by the laying on of hands. … In addition to serving as witnesses of Jesus Christ to all the world (Doctrine and Covenants 107:23), as Jesus’ apostles did, members of the current Quorum of the Twelve Apostles hold the keys of the priesthood—that is, the rights of presidency (Doctrine and Covenants 107:35; cf. 124:128)” (Encyclopedia of Mormonism , 1:59–60).
Joseph Fielding Smith, “The Quorum of the Twelve Apostles,” BYU Speeches
“Special Witness,” Lesson Helps for Teaching Children
“The Quorum of the Twelve Apostles,” BYU Speeches