1 Corinthians 14:7-9

American Standard Version

⁷ Even things without life, giving a voice, whether pipe or harp, if they give not a distinction in the sounds, how shall it be known what is piped or harped? ⁸ For if the trumpet give an uncertain voice, who shall prepare himself for war? ⁹ So also ye, unless ye utter by the tongue speech easy to be understood, how shall it be known what is spoken? for ye will be speaking into the air.