Un-translated tongues, like the bugle sound which no one has learned, do not communicate. If there had been anything like an unknown tongue, a tongue which no one spoke, speaking in that tongue would produce nothing but nonsense when the intent of speaking in other languages was to better communicate the gospel in their own language! Foreign tongues are just that—foreign!! In fact, the use of a foreign language would serve to SEPARATE rather than unite the people, for the speaker becomes a barbarian to the hearer!! Functionally, foreign tongues were a deterrent, not an aid to furthering the Word of God.
Paul transfers the idea of the useless-ness of untranslated languages from the general worship service, 1 Corinthians 14:13. Joined by the word wherefore, which always means “for this reason”, Paul reasons that the hearer that cannot understand what is prayed about cannot say “Amen” to what he cannot understand. Languages not known by the hearers do not communicate, and because the manifestations of the Spirit are for a ministry to others, a tongue-speaker must pray that he himself will translate, or else keep silent!, even if he is just praying!!
Here comes the dilemma most find themselves unable to understand in this chapter. “For if I pray”, translated “If unlikely I pray” in a tongue (language) my spirit prays, but my mind is unfruitful”. Immediately, Paul moves from the unlikely act to that that he would always do, “I shall pray with the spirit and I shall pray with the understanding (the mind understanding) also. I will sing with the spirit and I will sing with the mind also.” It mattered not if it were speaking, verse 2, praying, verse 13, or singing, verse 15; the intent was to TEACH, and that could not be done if the ones being taught could not understand the speaker. Paul is not jealous of those who spoke in tongues, he evidently could speak in more or different languages than all of them, he was showing how USELESS un-translated languages were to the church, and they taught no one. We have no record that Paul ever used anything but the vernacular language (and we know of him preaching, praying, and singing). We would not know he ever spoke in tongues if not for this statement, verse 18. The point of the chapter is that God has called us to be ministers to one another, teaching each other in song, preaching, or praying!!
“Be not children”, or quit acting like children—does Paul not infer that speaking in tongues that was not to the betterment of the congregation, childish?? “When I was a child, I spoke as a child” rings in our ears does it not? Isaiah 28:11, “For with stammering lips and another tongue will He speak to this people.” Isaiah speaks about God’s people not being mature enough to listen to the objective word of God being spoken. The preached word was not enough evidence to convince the Jew that God’s promises were sure. Jews were known to demand signs for belief (1 Corinthians 1:22), and in that attitude, they were like children who needed more than parents’ “:words” to convince them!! During the Isaiah an context, the people had turned their ears from the words of the prophets to the words of false priests who were proud and drunkards, Isaiah 28:1, 7-10 When we need more than God’s Word to believe His promises and power, faith is giving way to subjectivity. Then any word can get a hearing alongside God’s Word, depending upon which makes us “feel” better. “An appalling and horrible thing has happened in the land. The prophets prophesy falsely and the priests rule at their own authority. And My people live it so! But what will you do at the end of it?” Jeremiah 5:30 Needing MORE than God’s Word opens the door to Hell.