The Holy Ghost has appeared under the form of a dove, of fire, and of tongues, to signify His office in the Church.
“The Holy Ghost,” says St. Gregory the Great, “appeared in the form of a dove and of fire, because His work is done gently and zealously, and whoever is wanting in gentleness and zeal is not under His influence. He appeared in the form of tongues, because He gives to man the gift of speech, by which he may inflame others to the love of God.” The Holy Ghost appeared under the form of fire, because He consumes the dross of our sins, drives the darkness of ignorance out of our souls, melts the icy coldness of our hearts, and inflames us with love of God and of our neighbor, and because He hardens and strengthens the heart of man whom He has made from the clay of the earth. “Our God is a consuming fire.” (Heb. xii. 29.)