1 Corinthians 14:8-10

New Matthew Bible

⁸ And also, if the trumpet gives an uncertain call, who will prepare himself to fight? ⁹ So also likewise, when you speak with tongues, unless you speak words that have meaning, how can it be understood what is spoken? For you will be but speaking in the air.

¹⁰ Many kinds of voices are in the world, and none of them are without signification.