9 Thus 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.
10 There are, it may be, so many kinds of voices in the world, and none of undistinguishable sound.
11 If 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.
12 Thus ye also, since ye are desirous of spirits, seek that ye may abound for the edification of the assembly.
13 Wherefore let him that speaks with a tongue pray that he may interpret.
14 For if I pray with a tongue, my spirit prays, but my understanding is unfruitful.
15 What is it then? I will pray with the spirit, but I will pray also with the understanding; I will sing with the spirit, but I will sing also with the understanding.