Speaking in Tongues
- And again, I exhort you, my brethren, that ye deny not the gifts of God, for they are many; and they come from the same God. And there are different ways that these gifts are administered; but it is the same God who worketh all in all; and they are given by the manifestations of the Spirit of God unto men, to profit them.
- And again, to another, all kinds of tongues;
- And again, to another, the interpretation of languages and of divers kinds of tongues.
- And all these gifts come by the Spirit of Christ; and they come unto every man severally, according as he will.
- And I would exhort you, my beloved brethren, that ye remember that every good gift cometh of Christ (Moroni 10:8, 15-18).
- And again, it is given by the Holy Ghost to some to know the diversities of operations, whether they be of God, that the manifestations of the Spirit may be given to every man to profit withal.
- And again, it is given to some to speak with tongues;
- And to another is given the interpretation of tongues.
- And all these gifts come from God, for the benefit of the children of God (Doctrine and Covenants 46:16, 24-26). (See also, 1 Corinthians 12:10, 28, 30; 14.)
In Doctrine and Covenants 109:36 it says,
- Let the gift of tongues be poured out upon thy people, even cloven tongues as of fire, and the interpretation thereof.
"Tongues and their interpretation are classed among the signs and miracles which always attend the faithful and which stand as evidences of the divinity of the Lord's work. (See Mormon 9:24; Mark 16:17; Acts 10:46; 19:6.) Caution should always attend the use of the gift of tongues. 'It is not necessary,' for instance, 'for tongues to be taught to the Church particularly, for any man that has the Holy Ghost, can speak of the things of God in his own tongue as well as to speak in another; for faith comes not by signs, but by hearing the word of God.'" 
"Hearing the word of God" is the purpose for speaking in tongues. If understanding and the testimony of Christ does not increase, then the gift is being misused or is inspired by some other source than the Lord. Satan can speak in tongues. Joseph Smith said,
- Speak not in the gift of tongues without understanding it, or without interpretation. The devil can speak in tongues; the adversary will come with his work; he can tempt all classes; can speak in English or Dutch. Let no one speak in tongues unless he interpret, except by the consent of the one who is placed to preside; then he may discern or interpret, or another may. 
The Apostle Paul said,
- In the church I had rather speak five words with my understanding, that by my voice I might teach others also, than ten thousand words in an unknown tongue (1 Corinthians 14:19).
An example of speaking in tongues, but not through the power of God, was plainly manifest in February 2014, when the pastor of a snake-handling sect was killed after being bitten by a snake he was handling in a religious meeting. People at the meeting were supposedly feeling the Holy Ghost and were shouting and speaking in tongues at the meeting, which ended so badly.
Pentecost is a perfect example of the proper use of this gift (Acts 2:1-18). The apostles of the Lord spoke in their own tongue, but they were understood by thousands of pilgrims in their own tongues. On that day, the power of the Holy Spirit was manifest and many were converted.
In The Church of Jesus Christ of Latter-day Saints the gift of tongues is manifested every day among the thousands of missionaries serving around the world. Missionaries learn foreign languages and the interpretation thereof with astonishing ease, and words come to them that they have not mastered. The gift of tongues has also been manifest in other, singular events, such as at the dedication of the Kirtland Temple. But speaking in tongues is not a part of normal church meetings, such as sacrament meeting or testimony meeting.
- Teachings of Joseph Smith, pp. 148-149, as quoted by Bruce R. McConkie, Mormon Doctrine, Second edition, p. 801.
- Teachings of Joseph Smith, p. 162, 212.