1 Corinthians 14:9-12
9-12So if you speak in a way no one can understand, what's the point of opening your mouth? There are many languages in the world and they all mean something to someone. But if I don't understand the language, it's not going to do me much good. It's no different with you. Since you're so eager to participate in what God is doing, why don't you concentrate on doing what helps everyone in the church?
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.