Speaking in a tongue is the believer's external manifestation in the senses world of the internal reality and presence of the power of the holy spirit.
To speak to God divine secrets - 1 Corinthians 14:2
To speak the wonderful works of God - Acts 2:11
To magnify God - Acts 10:46
To pray perfectly - Romans 8:26,27
To give thanks well - 1 Corinthians 14:17
To have the Spirit bearing witness with our spirit - Romans 8:16
To know you are a joint-heir with Christ - Romans 8:17
To strengthen you with might in your inner man - Ephesians 3:16
To be a sign to unbelievers - 1 Corinthians 14:22; Mark 16:17
Rest to the soul - Isaiah 28:11,12; 1 Corinthians 14:21
Praying in the holy spirit
A believer operating the manifestation of the spirit called tongues will be edified spiritually, spiritually built-up. He can operate this manifestation in two situations: in public and in private. (1) The bulk of a believer's speaking in tongues is in his own private life. As such, speaking in tongues in private will be prayer or praise to the Father and, therefore is never interpreted. This prayer and praise is spoken of as "praying in the spirit." When you speak in tongues it is the spirit in you which is in direct communication with your heavenly Father, and as such your spirit is edified. (2) A believer can speak in tongues publicly in a believer's meeting. When a person publicly speaks in tongues, he must always interpret. A public message is never a prayer however; it is a communication from God meant for the people present. Both public and private speaking in tongues are called speaking to God.
Cortright
Homepage