Paul said those who speak in tongues speak to God and nobody understands them.
“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.” (1 Corinthians 14:2) (KJV 1900)
1Co 14:2 For he that speaks with a tongue does not speak to men but to God: for no one hears; but in spirit he speaks mysteries.
1Co 14:3 But he that prophesies speaks to men in edification, and encouragement, and consolation. Darby
1Co 14:2 Those who speak in strange tongues do not speak to others but to God, because no one understands them. They are speaking secret truths by the power of the Spirit.
1Co 14:3 But those who proclaim God's message speak to people and give them help, encouragement, and comfort. GNB
1Co 14:2 For the person who speaks in another language is not actually speaking to people but to God. Indeed, no one understands him, because he is talking about secrets by the Spirit.
1Co 14:3 But the person who prophesies speaks to people for their upbuilding, encouragement, and comfort. ISV
1Co 14:1 Pursue the love, and seek earnestly the spiritual things, and rather that ye may prophecy,
1Co 14:2 for he who is speaking in an unknown tongue—to men he doth not speak, but to God, for no one doth hearken, and in spirit he doth speak secrets;
1Co 14:3 and he who is prophesying to men doth speak edification, and exhortation, and comfort; YLT
In context Paul is comparing prophesy with tongues of the kind that are a prayer to God, and a mystery, which goes without interpretation most of the time. And His mind praying is unfruitful, but his prayers are heard for his edification. There is a point to tongues no one on Earth understands.