"O Lord, wishing to fulfill the mystery of Your economy..."

The Ascension of Christ, depicted with the Holy Trinity, the Preparation of the Throne, and various Saints (source)

  
O Lord, wishing to fulfill the mystery of Your economy, You took Your Disciples up to the Mount of Olives, and behold, You departed for the firmament of Heaven, You Who had become poor for me, and You were lifted up, therefore, You did not leave us, but You sent down Your All-Holy Spirit, to enlighten our souls.
-Idiomelon of the Stichera from the Great Vespers of the Ascension

(source)
  

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