"And I will put my Spirit in you..."

The Great Feast of Pentecost (source)

  
"And I will take you out from the nations, and will gather you out of all the lands, and will bring you into your own land:  and I will sprinkle clean water upon you, and ye shall be purged from all your uncleannesses, and from all your idols, and I will cleanse you.  And I will give you a new heart, and will put a new spirit in you: and I will take away the heart of stone out of your flesh, and will give you a heart of flesh.  And I will put my Spirit in you, and will cause you to walk in mine ordinances, and to keep my judgments, and do them.  And ye shall dwell upon the land which I gave to your fathers; and ye shall be to me a people, and I will be to you a God."
-Ezekiel 36:24-28, Read at the Great Vespers for the Feast of Pentecost
(source)
  

The Descent of the Holy Spirit at Pentecost (source)

  

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