Each evangelist is associated with his symbol, placed above him at the junction of the dome and the barrel: the eagle for John, the lion for Mark, the bull for Luke and the angel for Matthew. These figures emanate from the vision of the glory of God in the book of the prophet Ezekiel, in which they form the "four living beings" or tetramorph, also present in the Apocalypse of John. The Fathers of the Church applied these symbols to the Evangelists, whether they accompany or replace them.
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