Be swift my soul to answer,
Be jubilant my feet,
Saint Augustine wrote about what he called “jubilation”:
See how he himself provides you with a way of singing. Do not search for words, as if you could find a lyric which would give God pleasure. Sing to him “with songs of joy.” This is singing well to God, just singing with songs of joy.
But how is this done? You must first understand that words cannot express the things that are sung by the heart. Take the case of people singing while harvesting in the fields or in the vineyards or when any other strenuous work is in progress. Although they begin by giving expression to their happiness in sung words, yet shortly there is a change. As if so happy that words can no longer express what they feel, they discard the restricting syllables. They burst out into a simple sound of joy, of jubilation. Such a cry of joy is a sound signifying that the heart is bringing to birth what it cannot utter in words.
Now, who is more worthy of such a cry of jubilation than God himself, whom all words fail to describe? If words will not serve, and yet you must not remain silent, what else can you do but cry out for joy? Your heart must rejoice beyond words, soaring into an immensity of gladness, unrestrained by syllabic bonds . Sing to him with jubilation.
– Augustine in Commentary on Psalm 32
In her PhD dissertation, Heidi Baker wrote:
The primary purpose of prayer in tongues is to serve as extraordinary communication with God and from God to humanity. This must mean that Pentecostal glossolalic prayer, theologically understood, may not be viewed as human capability utilized at will to achieve some religious end. Like all true encounters with God, it takes place primarily as the consequence of the divine resolution to act. The closer one draws to the divine mystery, the more pressing it becomes to express oneself, and simultaneously the less capable one is to achieve sufficient expression. This is the climax which glossolalic prayer breaks forth.