(OSV News) -- Of all the great Christian feasts, none, with the exception of Easter and perhaps Christmas, has been and is more widely celebrated than Pentecost.

The oldest of our festivals, just the name stirs up fervor and anticipation among the faithful. At Christmas, we celebrate the miracle of the Incarnation, at Easter the miracle of the Resurrection, and now at Pentecost, the miracle of the coming of the Holy Spirit, the third person of the Trinity.

Father K. Krogh-Tonning, in his book "Catholic Christianity and the Modern World" (1916), likens Christmas, Easter and Pentecost "to three precious stones of equal beauty." He asks, "But what would Easter be without Pentecost? What significance would our Lord's death and resurrection have had for us without the Holy Ghost who alone can bring us to Christ?"

The Holy Spirit is mentioned throughout the Bible: at the Annunciation, at Jesus' baptism, at the Visitation, during the Transfiguration, in the Upper Room following the Resurrection. Our Lord told his apostles, "And I will ask the Father and he will give you another Advocate to be with you always, the Spirit of truth, which the world cannot accept, because it neither sees nor knows it. But you know it, because it remains with you, and will be in you" (Jn 14:16-17). At his ascension, Jesus charged the apostles to remain in Jerusalem, "until you are clothed with power from on high" (Lk 24:49).

So the apostles stayed in the city praying together throughout the nine days from the Ascension until the feast of Pentecost. This extended prayer period would become the first and model "novena."

On Pentecost, Jesus' followers were gathered together in the Upper Room, likely uncertain as to exactly what they were waiting for. Jesus had said he would eventually leave them and send the Holy Spirit, which he also called the Advocate, Counselor, Paraclete, Spirit of Truth. Now, he would keep his promise. But what was the nature of the Holy Spirit, and how would that Spirit be manifested to them?

On Pentecost, they found out.

The Holy Spirit came in the form of "tongues of fire" accompanied by "a noise like a strong driving wind" (Acts 2:3, 2). This scene is reminiscent of the thunder, lightning and smoke that occurred when God gave Moses the stone tablets on Mount Sinai and when God spoke from heaven and the dove descended during Christ's baptism. These events signaled new beginnings.

Pentecost is also a new beginning: The Church received its universal mission on that day. That mission had previously been described to the apostles by Jesus, "Go, therefore, and make disciples of all nations, baptizing them in the name of the Father, and of the Son, and of the Holy Spirit" (Mt 28:19). This was and still is a clear message -- a clear mission -- to all Christians.

The followers of Jesus now had a new relationship with him. He was no longer with them visibly but filled their hearts and their souls with the Holy Spirit, who stays with each of us forever.

Through all the centuries and into eternity, the Holy Spirit manifests himself to us not by tongues of fire but by our baptism.

The Holy Spirit descended on the apostles, and these men who had once deserted Jesus, who had been fearful to speak his message, now found courage and enthusiasm to witness in his name. Entering into their ministry of preaching, they no longer hid in fear, were no longer intimidated by others, but would walk in the light of Christ proclaiming the Good News, making known the new covenant.

On the day of Pentecost, the apostles, led by Peter, began to preach to those gathered in Jerusalem, and no matter that there were many people speaking different languages, those listening heard what the apostles said in their own language. They wondered if the apostles were drunk, "filled with new wine," asking, "Then how does each of us hear them in his own native language?" (Acts 2:13, 8). So inspired by the words of Peter, 3,000 people were converted that day. Motivated by the Holy Spirit, the apostles would go out to call people everywhere to conversion, to accept the King of Glory.

Pentecost comes from a Greek word, "pentekoste," meaning 50. That our Christian feast of Pentecost is 50 days after the Resurrection, culminating the Easter season, is not by chance.

Pentecost was an ancient Jewish holiday during which the Hebrews celebrated the wheat harvest. That celebration was also known as the Feast of Weeks, which, in accordance with the Old Testament Book of Leviticus, was to be commemorated 50 days after the Passover. Jewish tradition holds that Moses was given the Ten Commandments 50 days after the original Passover, when the Israelites escaped Egyptian bondage.

On our liturgical calendar, the earliest day for the Pentecost celebration is May 10; this year, Pentecost is celebrated May 19. All Sundays from the end of Eastertide until Advent are counted from this feast -- for example, the second Sunday of Pentecost, etc. -- signaling the importance the church places on Pentecost.

A vigil, similar to the Easter Vigil, was for centuries held before Pentecost. During that vigil, baptism was conferred on anyone seeking to join the church but, for different reasons, had not participated at the Easter Vigil. It was a "kind of makeup" for those who might have been ill, not properly prepared, traveling at Easter, etc. On Pentecost Sunday, those baptized the night before wore their white baptismal garments to church, and the day is often referred to as "Whitsunday" (White Sunday).

Until the 20th century, an octave had long been connected to Pentecost. The church gave us seven more days (an octave) to grasp what had happened in the Upper Room. In 1969 as part of an effort to streamline the liturgical year, the Vatican removed the Pentecost octave from the church calendar.

Today, the church's General Norms of the Liturgical Year includes Pentecost as part of the 50 day Easter season, connecting Easter, the Ascension and Pentecost. "These days are celebrated in joyful exultation as one feast day, or better 'one great Sunday.'" That inclusion in no way diminishes the great feast of Pentecost.

- - - D.D. Emmons writes from Pennsylvania.