So....first the fire appeared to them as cloven tongues, then it sat upon them, then they were filled with the Holy Spirit.
This is now coming upon you also, and that to strip away and consume your sins which are like thorns, and to brighten yet more that precious possession of your souls, and to give you grace; for He gave it then to the Apostles.The power of the Holy Spirit, which is bestowed upon him who loves God and keeps His commandments, does not appear visibly in the form of fire, nor does it come with a loud sound like a violent wind - for this happened only in the time of the Apostles for the sake of the unbelievers.Instead, it is seen spiritually in the form of spiritual light, and comes with all calm and joy. Guide to Byzantine Iconography, Vol. 1, by Constantine Cavarnos (Also found at http://www.orthodox.net/gleanings/pentecost.html)
What a great day to commemorate, the birth of the Church as we know it, it says on the day of Pentecost the disciples were filled with the Holy Spirit (Acts 2:4), and the apostle Peter preached his first sermon, urging the crowds to repent, to believe in Jesus Christ as their Messiah and to receive the gift of the Holy Spirit (verse 38). That very day of Pentecost some 3,000 people were baptized and became the people of God (verse 41). The church had been born.
In my search to my pondering regarding Pentecost I found a great resource, Lecture XVII.Continuation of the Discourse on the Holy Ghost. http://www.ccel.org/ccel/schaff/npnf207.ii.xxi.html



