"In reality," what happened is exactly what the Evangelists recount. The divine nature of the Lord Jesus Christ became visible to the apostles. At the same time, they saw that all the Law and the Prophets—the entire religious tradition of the Old Testament—were united before Christ in the persons of Moses and Elijah, speaking with Christ about His Passion.

The purpose of the Transfiguration, as far as we can discern from the Evangelists' accounts, was primarily to confirm the closest disciples in the faith and confession that Peter had just proclaimed, namely, to affirm to them that Jesus of Nazareth is indeed the Messiah-Christ anticipated since the days of Moses. Moreover, and perhaps more importantly, the Lord allowed the disciples to behold His glory as God so that, when they would see Him being crucified, they might understand that He suffers voluntarily, and proclaim to the world that He is truly the radiance of the Father. Thus, the "purpose" of the Transfiguration was to prepare the disciples to comprehend the mystery of the Sacrifice on the Cross.

The gift of "speaking in tongues", "praying in tongues", or simply the "gift of tongues", in Greek "glossolalia" — is one of the many gifts of the Holy Spirit, which is given for edification in the faith and the growth of the Church. In different eras and in different parts of the Church, this gift manifests itself in various ways; at times it may become unnoticeable or noticeably transformed. This is natural, for the gifts of the Holy Spirit are always given with a specific purpose — "for the edification of the Church". Nevertheless, it can be said that in one form or another, this gift is always present in the Church.

We know of at least three main varieties of this gift.

First, there is the gift of speaking in a language unknown to the speaker. This is how the apostles spoke on the day of Pentecost. This is how, quite often, preachers and missionaries speak, and their word reaches the hearts of the listeners. It is essential that this form of glossolalia occurs if and only if a person is speaking about Jesus Christ, His Cross, and Resurrection. At present, this gift is quite rare.

Second, glossolalia may be expressed when a person in prayer praises God in a language that does not exist among the nations of the Earth. This is usually called "tongues of angels". Love for God, reverence before Him, and adoration of Him encompass at this moment not only the person's heart, but also their mind and emotional sphere... And suddenly the prayer is poured out in words incomprehensible to the person themselves. According to the testimony of early Christians, the Holy Spirit simultaneously grants another person the gift of interpretation, so that "the church may receive edification". This gift is currently widespread enough to be a noticeable phenomenon in the Church.

However, in our time, the gift of interpretation is much less common. Perhaps this is related to the fact that the edification of the modern Church is carried out differently than in the ancient one. To understand this gift, it is important to keep a few points in mind. Speaking in tongues of angels is given, as a rule (though not always), through the prayer of other Christians — those who possess this gift. Furthermore, the speaker usually does not understand the meaning of their own words. They are aware only of a certain non-verbal sense of the prayer in which they began speaking in such a language. In different parts of the Church there is a certain continuity, so that by the way glossolalia manifests in a person's prayer, one can quite accurately discern in which Church they received this gift. The glossolalia of Pentecostals is not the same as that of Catholics, and the glossolalia of Lutherans differs from that of the Orthodox. Often, such glossolalia sounds like a language unknown to humanity. Most commonly, this glossolalia (across all denominations) is compared to ancient Hebrew or Aramaic. Perhaps the Holy Spirit engages some aspects of the person's personality that are unknown to us... It is fundamentally important that this form of glossolalia is given during prayer and for prayer, usually — for the glorification of God.

Third, there is another form of glossolalia closely connected to the previous one. This should rather be called non-verbal prayer. The Apostle Paul speaks of this, saying that the Holy Spirit intercedes for us with groanings which cannot be uttered. This prayer differs from the previous form in that distinct speech elements (words, phrases) are not always discernible in it, and in that such a prayer is sung rather than spoken. Often it is born as a continuation (and intensification) of our usual prayer and psalmody. In this, the Holy Spirit allows our heart to break out beyond the limits of human language and turn to God in some other, highly personal, yet non-verbal way.

Since ancient times, this prayer-glossolalia predominantly occurred during divine services. It was such an ordinary occurrence that church liturgical rubrics of the second half of the first millennium even designate moments in the service when this gift of the Holy Spirit typically manifests in the community. Some Orthodox typicons, including Russian ones, retained such instructions right up until the end of the 15th century. Generally speaking, however, since the end of the first millennium, this form of glossolalia has largely transitioned into the realm of church musical creativity.

Since the end of the 19th century, in various parts of the Church, the Holy Spirit has begun to explicitly bestow these gifts anew, albeit in different ways. This is likely due to the fact that different Churches have "dried up" to varying degrees in theological theorizing and have lost the experience of a living connection with the Spirit. It is perhaps for our edification in this regard that the Lord renews these gifts of His within us.

It is important to note in conclusion that the only gift of the Holy Spirit that is absolutely indispensable for the life of the Church, without which She cannot exist, is the gift of love. All else is given as the need arises...