"The post-festal and final feast, let us celebrate with joy..."

The Great Feast of Pentecost (source)

  
The post-festal and final feast, let us celebrate with joy, this is Pentecost, the fulfillment and consummation of the promise, on which the fire of the Paraclete straightaway descended upon the earth in the form of tongues, and enlightened the Disciples, and showed them to be mystics of Heaven. The light of the Paraclete has come, and has enlightened the world.
-Kathisma of the Orthros for Pentecost

(source)
  

Through the prayers of our Holy Fathers, Lord Jesus Christ our God, have mercy on us and save us! Amen!