Now, brothers, if I come to you speaking in tongues, how will I benefit you unless I bring you some revelation or knowledge or prophecy or teaching? If even lifeless instruments, such as the flute or the harp, do not give distinct notes, how will anyone know what is played? And if the bugle gives an indistinct sound, who will get ready for battle? So with yourselves, if with your tongue you utter speech that is not intelligible, how will anyone know what is said? For you will be speaking into the air. There are doubtless many different languages in the world, and none is without meaning, but if I do not know the meaning of the language, I will be a foreigner to the speaker and the speaker a foreigner to me. So with yourselves, since you are eager for manifestations of the Spirit, strive to excel in building up the church.
Therefore, one who speaks in a tongue should pray that he may interpret. For if I pray in a tongue, my spirit prays but my mind is unfruitful. What am I to do? I will pray with my spirit, but I will pray with my mind also; I will sing praise with my spirit, but I will sing with my mind also. Otherwise, if you give thanks with your spirit, how can anyone in the position of an outsider say “Amen” to your thanksgiving when he does not know what you are saying?
Comment: The ‘I’ at the beginning probably doesn’t just refer to Paul but to anyone who comes to speak to (teach, preach, evangelise) a body of believers. A musical instrument needs to play the correct tune or else it is just making noises. Paul is not here speaking against the practice of speaking in tongues but says that people need to worship both in spirit and with their mind.
Paul says ‘strive to excel in building up the church’. He also addresses the people who are not believers and says ‘how can anyone in the position of an outsider say “Amen” to your thanksgiving when he does not know what you are saying?’ People coming to faith depends upon a number of things – the call of God, their choosing to respond – but here Paul is emphasizing that Christianity isn’t a blind leap into the unknown but is a real commitment to time/space facts. Therefore the speaker must be clear in plain speech or through interpretation!
Prayer: Please, my Father, strengthen my life so that in both my actions and in my speaking I may be true to you and understandable to those watching how I live.
As I read it! 