See also: D&C 88:70
Solemn assemblies were restored in this dispensation as a part of the “restitution of all things, which God hath spoken by thy mouth of all his holy prophets since the world began.” (Acts 3:21.) In ancient Israel, these assemblies were held in connection with feasts, sacrifices, and the dedication of Solomon’s Temple. On these solemn occasions, Israel gathered and came before the Lord in a state of ritual holiness. — “I Have a Question” Ensign, December 1988
Brothers and sisters, President Hinckley has requested that I now handle the business of the solemn assembly for which we are met. This is an occasion of great significance for members of The Church of Jesus Christof Latter-day Saints throughout the world. We shall vote by quorums and groups. Wherever you are, you are invited to stand when requested and express by your uplifted hand whether you choose to sustain those whose names will be presented. Those who are standing when appropriately called upon would be the ones who would be given the privilege to vote.
The General Authorities assigned to the Assembly Hall on Temple Square or the Joseph Smith Memorial Building will observe the voting in those gatherings. In stake centers, a member of the stake presidency will observe the voting. Should there be any negative votes, we ask that we be so advised. We shall now proceed with the business of this solemn assembly. — President Thomas S. Monson, “The Solemn Assembly Sustaining of Church Officers,” General Conference, April 1995
We are met in the Tabernacle on Temple Square, Salt Lake City, in a formal Solemn Assembly of the body of the Church to express the voice of the Church in a first sustaining vote for a new president of the Church. This proceeding is in accordance with the practice of the Church from the first sustaining vote cast by a general conference for President John Taylor, until the present time. — N. Eldon Tanner, “The Solemn Assembly,” General Conference, April 1974