1 Corinthians 14:7-12

7Even lifeless things giving a sound, whether pipe or harp, if they give not distinction to the sounds, how shall it be known what is piped or harped?

8For also, if the trumpet give an uncertain sound, who shall prepare himself for war?

9Thus also ye with the tongue, unless ye give a distinct speech, how shall it be known what is spoken? for ye will be speaking to the air.

10There are, it may be, so many kinds of voices in the world, and none of undistinguishable sound.

11If therefore I do not know the power of the sound, I shall be to him that speaks a barbarian, and he that speaks a barbarian for me.

12Thus ye also, since ye are desirous of spirits, seek that ye may abound for the edification of the assembly.