2 Those who speak in a tongue14:2. This is clearly not the use of normal human language. There is much debate over this phenomenon. Clearly the early church was gifted with the ability to speak and be understood in different human languages as Acts 2 makes clear. However, some kind of "ecstatic utterance" appears to be in view here. Its practice in Corinth was being abused, and so Paul has to counteract the problem here. are not talking to people, but to God, because nobody can understand them as they speak mysteries in the Spirit. 4 Those that speak in a tongue only build themselves up, but those who speak God’s message build up the church. I would like it if you all spoke in tongues, but I’d prefer if you could speak God’s message.
14 For if I pray out loud in a tongue, my spirit is praying, but it does nothing for my understanding!
15 So then, what should I do? I will pray "in the Spirit," but I will pray with my mind too. I will sing "in the Spirit," but I will sing with my mind too.14:15. Paul here seems to be using the phraseology of some of those in Corinth who were proud of being "in the Spirit" as if that was superior to anything else. Paul points out that being "in the Spirit" is not helpful unless it produces understanding.