Rom_8:26 Likewise the Spirit also helpeth our infirmities: for we know not what we should pray for as we ought: but the Spirit itself maketh intercession for us with groanings which cannot be uttered.
A great problem in using this verse to make sense of the babbling nature of tongue-speaking is that this is not something only promised to those who speak in tongues. This is something promised to all believers who have the Holy Spirit, who moves us to pray and gives us words to speak.
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The issue I have with that verse is that if the groanings are too deep for words to express, that would and should, include tongues.
Now, most people who speaking tongues SAY “words”, therefore if the groanings are too deep for words to express, that must by default, include tongues as that is *words* and a *language*.
Therefore, I cannot accept that verse as support for a prayer language.
The point is that God understands what is being expressed. The Jews in Acts 2 did hear the apostles speak (laleō, to utter words) by other tongues (glōssa, the tongue, by by implication a language) in their own language, (dialektos, dialect), but 1Cor. 14 refers to glōssa in which only God understands, and it takes a gift to understand, not natural ability.
Whether we can test this as having the characteristics of language or not, they did have it, but as we cannot test what they spoke in 1Cor. 14, then we cannot compare it to today, or at least every case.
But we can discern what love is, with its actions, and this lack of love for holiness, lost souls, and each other in body language is one the world can understand. That is what needs to be the focus more than tongues, and determines the use and efficacy of gifts given to express God.