The happy day has dawned for us on which Holy Church makes her first radiant appearance to the eyes of faith and sets the hearts of believers on fire. It is the day on which we celebrate the sending of the Holy Spirit by our Lord Jesus Christ, after he had risen from the dead and ascended into glory.
In the Gospel it is written: “If anyone is thirsty, let him come to me and drink. Whoever believes in me, rivers of living water shall flow from his heart.” The Evangelist explains these words by adding: “Jesus said this about the Spirit which those who believed in him were to receive. For the Spirit had not yet been given because Jesus had not yet been glorified.” Now the glorification of Jesus took place when he rose from the dead and ascended into heaven, but all was not yet accomplished. The Holy Spirit still had to be given; the one who made the promise had to send him. This is precisely what occurred at Pentecost.
After being in the company of his disciples for the forty days following his resurrection, the Lord ascended into heaven, and on the fiftieth day—the day we are now celebrating—he sent the Holy Spirit. The account is given in Scripture: Suddenly a sound came from heaven like the rush of a mighty wind, and there appeared to them tongues like fire which separated and came to rest on each one of them. And they began to speak in other tongues, as the Holy Spirit gave them power of utterance. (Acts 2:2) That wind cleansed the disciples’ hearts, blowing away fleshly thoughts like so much chaff. The fire burnt up their unregenerate desires as if they were straw.
The tongues in which they spoke as the Holy Spirit filled them were a foreshadowing of the Church’s preaching of the Gospel in the tongues of all nations. After the flood, in pride and defiance of the Lord, an impious generation erected a high tower and so brought about the division of the human race into many language groups, each with its own peculiar speech which was unintelligible to the rest of the world. At Pentecost, by contrast, the humble piety of believers brought all these diverse languages into the unity of the Church. What discord had scattered, love was to gather together. Like the limbs of a single body, the separated members of the human race would be restored to unity by being joined to Christ, their common head, and welded into the oneness of a holy body by the fire of love.
Anyone therefore who rejects the gift of peace and withdraws from the fellowship of this unity cuts himself off from the gift of the Holy Spirit.
So then, my fellow members of Christ’s body, you are the fruits of unity and the children of peace. Keep this day with joy, celebrate it in freedom of spirit, for in you is fulfilled what was foreshadowed in those days when the Holy Spirit came.
At that time whoever received the Holy Spirit spoke in many languages, individual though he was. Now in the same way unity itself speaks through all nations in every tongue. If you yourselves are established in that unity you have the Holy Spirit among you, and nothing can separate you from the Church of Christ which speaks in the language of every nation of the world.
St Augustine of Hippo