1 Corinthians 14:6-19, especially vs. 19: "yet in the church I would rather speak five words with my understanding, that I may teach others also, than ten thousand words in a tongue." The phenomenon of speaking in tongues appeared among Christians during the earliest days, being reported in the Acts of the Apostles (Acts 10:46; 19:6) as well as here in First Corinthians. But soon after, tongue-speaking was known among the Montanists, a sect of heretical Christian in Phrygia that flourished from the 2nd to the 9th century.
Further, the phenomenon has not been limited to Christians, for both Plato, among the pagan Greeks, and Virgil, among the ancient Latins, tell of tongue-speaking in various pagan rites. During the Middle Ages in Europe, tongues was practiced by the mendicant friars and later by early Quakers and Methodists. The practice enjoyed such a revival during the 19th and 20th centuries among some Evangelical Protestant congregations, that whole denominations formed, distinguished principally by tongue speaking. In the twentieth century, tongues even spread among many "mainline" western Churches, including Anglicans and Roman Catholics.
The Apostle Paul himself spoke in tongues, considering it a gift from God for which he gave thanks (1 Cor. 14:18). However, in today's reading, as St. Paul speaks about this practice, we can discern his cautions concerning tongue speaking.
A reading through the passage immediately discloses the Apostle's point of view, that this vocal gift from the Holy Spirit (vss. 12,18) ought to be a matter of private prayer and avoided in public, corporate worship (vss.6,9,19). His reasoning is quite straightforward: there are "many kinds of languages in the world" (vs. 10), and if one does "not know the meaning of the language" he is made a foreigner simply because he cannot understand what he hears (vs.11).
But observe also: the present passage rejects the opinion of those who relegate speaking in tongues to merely psychological causes. Such opinions disregard St. Paul's manifest assumption that tongues can be a gift of the Holy Spirit (vss. 12,18). However, while God the Holy Spirit may give tongues, He also will give the "discernment of spirits" (1 Cor. 12:10). Note also, evidence from comparative religions suggests that not all speaking in tongues is of God. Some does indeed come from demonic sources and from darkened or immature human psyches.
As an Apostle, St. Paul was one sent by the Lord Jesus, a man under necessity to preach the Gospel and at grave spiritual risk for refusing to do so (1 Cor. 9:16). Today's passage clearly shows the unceasing urgency in him to communicate the good news. Hence, St. Paul was deeply concerned for understanding among his hearers, a concern that included occasions when he prayed with other people, especially in worship with those new to the Faith (vss. 6,9,11,16).
Continually planting churches in communities where the Christian message never had been heard, St. Paul bore a responsibility for these congregations he brought into existence - as in the case of the church at Corinth. The present passage reveals his concern for such congregations - that they develop as communities wherein their members would grow in spiritual knowledge - again, that primary concern for edification (vss. 12,19) and the insistence that tongues should remain a matter of private devotions, so as not to confuse congregations.
Following the Apostle's concern that prayer, hymns, and blessings should be understood (vss. 15,16), the Orthodox Church in its worship continues to resist the introduction of tongues into corporate worship, fearing it might confuse the understanding of the Faithful.
Light is the Father; and Light the Son; Light is the Holy Spirit descending upon the Apostles through which the whole universe was illuminated to worship the Holy Trinity.