Paul said those who speak in tongues edified themselves only, unless they interpret, so others can understand and be edified. This means first century tongue speakers understood what they were saying and were edified. This proves today's claims to the gifts are fraudulent because nobody claiming the gift of tongues knows what they are saying.
According to two different tongues speakers I have known who experience tongues occasionally in private prayer, they know what they are praying -- although not always expressed in rational thought, but in emotional utterance -- although they do not understand the words they are expressing with their lips. Both persons, from very different backgrounds, had quite similar experiences.
On July 4, 1987, I was part of an interdenominational evangelism team that was doing outreach to all of the July 4 revelers on Stewart Beach on Galveston Island. As part of our ministry, we had a first aid tent and passed out water so that people would not get dehydrated. I left the beachfront with a friend to fetch another large cooler of chilled bottled water from our church bus, and on the long walk back, we walked by a bus that was being used for prayer. Standing outside the bus was a woman praying in tongues. I made some sort of unkind comment about her tongue-speaking to my friend, who was listening to her quite thoughtfully. A moment later, he asked if I could understand what she was saying. I told him that I obviously couldn't, she was babbling. He said that he could. He could hear her sounds, but also hear words in English at the same time. He said, "She is praying specifically for ______ (a man we knew who helped organize the event) because he is confronting a demonized man right now."
That sounded very strange to me. We had seen lots of drunkeness and bad behavior, but nothing like a demonized person. I said, "That's weird." About three or four minutes later, we finally got to the first aid tent with the heavy cooler and _______ was confronting a man with 666 tattooed on his forehead and hand, who had been screaming blasphemies at the group. _______ had commanded him to silence in the name of Jesus, but the man didn't want to hear the gospel. _______ ordered the man in the name of Jesus to leave us alone, and the man left.
(1) Neither one of us had seen this man before, and the whole thing apparently started about 5 minutes after we left.
(2) I heard nothing but babbling when the woman was praying. My only source of information was my friend who apparently interpreted the woman's prayer, who also did not know about the man and who had never experienced the gift of interpreting tongues and did not practice speaking in tongues. In fact, he thought tongues-speaking was quite strange. Moreover, in the next 10 years of being in close association with him, he did not dabble in speaking in tongues, nor associate with many charismatic Christians.
I do not speak in tongues, nor wish to speak in tongues. I don't encourage people to speak in tongues. I also don't think that most modern expressions of tongue-speaking are biblical or valid. If it is done in a public meeting, it needs to be interpreted, and the congregation can determine for themselves if the interpretation is from God.
Yet, based on the scripture and based on a few experiences I have had, as well as similar experiences I have heard from a few trusted and mature Christians, I do not discount any of the "sign gifts" out of hand. God may indeed use them from time to time for His purposes.
NE IN SCRIPTURE SOUGHT to speak in tongues but it was GIVEN and that is why it was not given to all Christians (1 Cor. 12:29-30).