WHEN THE DAY OF PENTECOST HAD COME, the disciples were all together in one place. And suddenly from heaven there came a sound like the rush of a mighty wind, and it filled the entire house where they were sitting. Divided tongues that seemed like fire appeared among them, and a tongue rested on each of them. All of them were filled with the Holy Spirit and began to speak in other languages, as the Spirit gave them ability. Now there were devout Jews from every nation under heaven staying in Jerusalem. And at this sound the crowd gathered and was bewildered, because each one heard the disciples speaking in the native language of each. Amazed and astonished, they said to one another, “Behold, are not all these who are speaking Galileans? And how is it that we hear them speak in our own native language? Parthians, Medes, Elamites, and residents of Mesopotamia, Judea and Cappadocia, Pontus and Asia, Phrygia and Pamphylia, Egypt and the parts of Libya belonging to Cyrene, and visitors from Rome, both Jews and proselytes, Cretans and Arabs – in our own languages we hear them speaking about God’s works of power.”
Saint Gregory the Theologian comments on the gradual illumination of Christ's disciples,
So that by gradual increase and progress from glory to glory, the light of the Trinity might shine upon the more illuminated, for this reason it was, I think, that He gradually came to dwell in the disciples. He measured Himself out to them according to their capacity to receive Him: at the beginning of the gospel, then after the Passion, then after the Ascension, making perfect their powers, being breathed upon them, and then appearing in fiery tongues at Pentecost. You see lights breaking upon us, gradually, and knowledge of such order of theology, as is better for us to maintain, neither proclaiming things too suddenly, nor yet keeping them hidden to the end. He said that all things should be taught us by the Spirit Himself, made clear at a later time, when such knowledge would be seasonable and capable of being received after our Savior's restoration; when it would no longer be received with incredulity because of its marvelous character. For what greater thing than this did either He promise, or the Spirit teach. If He is not to be worshiped, how can He deify me by baptism? And indeed from the Spirit comes our new birth, and from the new birth our new creation, and from the new creation our deeper knowledge of the dignity of Him from whom it is derived. Look at these facts: Christ is born; the Spirit is His forerunner. He leads Him up. He works miracles; the Spirit accompanies them. He ascends; the Spirit takes His place.