Augustine of Hippo

Both in the prophet Ezekiel and in the Apocalypse of the same John whose Gospel this is, there is mentioned a quadruple beast, having four characteristic faces: a man's, a calf's, a lion's, an eagle's. Very many who have commented on the mysteries of the holy Scriptures before us have understood the four Evangelists in this animal, or rather in these animals. The lion, [they say], has been put for king, because the lion seems to be, in a way, the king of beasts because of his power and terrifying bravery. This character has been attributed to Matthew because he described in proper order the royal line in the generations of the Lord, how the Lord was through royal descent from the seed of King David. But Luke, because he began from the priesthood of the priest Zechariah, making mention of the father of John the Baptist, is accounted the calf because the calf was the important victim in the sacrifice of the priests. Christ as a man has rightly been assigned to Mark, because neither did he say anything about his royal power nor did he begin from the priestly, but he simply started with Christ the man. All of these have practically not departed from the earthly things, that is, from those deeds that the Lord Jesus Christ performed on earth. They said very few things about his divinity, as if they were walking with him on earth. There remains the eagle: it is John, he who preaches the sublime and who gazes with unflinching eyes upon the internal and eternal light.