Pentecost is a remembrance of when the Holy Spirit was poured out to Jesus' disciples after his ascension into heaven. The Holy Spirit came to them in the sound of a rushing wind, and in tongues of flame.

When the day of Pentecost came, they were all together in one place. Suddenly a sound like the blowing of a violent wind came from heaven and filled the whole house where they were sitting. They saw what seemed to be tongues of fire that separated and came to rest on each of them.
Acts 2:1-3

On that day alone, three thousand were converted to the Christian faith. They formed the Christian church, and worked diligently to spread the word of God to all people. Through their original work Church has grown to the point it is at today. We pray asking for the fervor for spreading the word that the first Christians had.