9 This is the Spirit that at the beginning “moved upon the waters;” by whom the world moves; by whom creation consists, and all things have life; who also wrought mightily in the prophets, and descended in flight upon Christ. This is the Spirit that was given to the apostles in the form of fiery tongues. This is the Spirit that David sought when he said, “Create in me a clean heart, O God, and renew a right spirit within me.” Of this Spirit Gabriel also spoke to the Virgin, “The Holy Ghost shall come upon you, and the power of the Highest shall overshadow you.” By this Spirit Peter spoke that blessed word, “You are the Christ, the Son of the living God.” By this Spirit the rock of the Church was established. This is the Spirit, the Comforter, that is sent because of you, that He may show you to be the Son of God.
Source: Discourse on the Holy Theophany (New Advent)