1 Corinthians 14:2

2 For anyone who speaks in a tonguea does not speak to people but to God. Indeed, no one understands them; they utter mysteries by the Spirit.

Read 1 Corinthians 14:2 Using Other Translations

For he that speaketh in an unknown tongue speaketh not unto men, but unto God: for no man understandeth him; howbeit in the spirit he speaketh mysteries.
For one who speaks in a tongue speaks not to men but to God; for no one understands him, but he utters mysteries in the Spirit.
For if you have the ability to speak in tongues, you will be talking only to God, since people won’t be able to understand you. You will be speaking by the power of the Spirit, but it will all be mysterious.