1 Corinthians 14:13-17
13-17So, when you pray in your private prayer language, don't hoard the experience for yourself. Pray for the insight and ability to bring others into that intimacy. If I pray in tongues, my spirit prays but my mind lies fallow, and all that intelligence is wasted. So what's the solution? The answer is simple enough. Do both. I should be spiritually free and expressive as I pray, but I should also be thoughtful and mindful as I pray. I should sing with my spirit, and sing with my mind. If you give a blessing using your private prayer language, which no one else understands, how can some outsider who has just shown up and has no idea what's going on know when to say "Amen"? Your blessing might be beautiful, but you have very effectively cut that person out of it.
18-19I'm grateful to God for the gift of praying in tongues that he gives us for praising him, which leads to wonderful intimacies we enjoy with him. I enter into this as much or more than any of you. But when I'm in a church assembled for worship, I'd rather say five words that everyone can understand and learn from than say ten thousand that sound to others like gibberish.