Revelation 4:7

Each of the animals is associated with one of these elements: the lion with fire, due to the animal's warmth and spirited nature; the calf with the earth, because the calf's work is connected to the soil; the man with the air, as humans are celestial and transcendent beings due to the artfulness [λεπτότητα] of the mind; and the eagle with water, since birds originate from water. Around the throne of God are seen those deemed worthy of care and providence, signified through living beings, that is, those on earth.

And the first living creature was like a lion, etc. These living creatures are interpreted in various ways. But blessed Augustine, according to the order of this book, says that Matthew is understood in the lion, who narrates the royal lineage of Christ, who also conquered as the Lion of the tribe of Judah. For the cub of the lion is Judah (Gen. 49). And in whom, as a king, he is feared by a king, worshipped by the magi. Where also the king reckons with his servants, the king makes a marriage for his son, and finally, the king separates the sheep from the goats. Luke is in the calf, which was a great sacrifice in the law. For not only are his beginnings around the temple and sacrifices, but it also concludes: And they were continually in the temple praising and blessing God (Luke 24). The face of a man signifies Mark, who, saying nothing of the royal or priestly power of the Lord, simply narrates the deeds of the man Christ. But John is the eagle, who sharply looks at the birth of the Word like the rising sun. The living creatures sometimes signify the evangelists, sometimes the whole Church. Whose strength is shown in the lion, sacrifice in the calf, humility in the man, sublimity in the flying eagle.

And the first living creature was like a lion: and the second living creature like a calf: and the third living creature, having the face, as it were, of a man: and the fourth living creature was like an eagle flying. We should ask the question of why John said that the first living creature was like a lion while Ezekiel says that the appearance of man was in the first animal. So, either the historical order (which the mystical words of the Scriptures do not always keep) has been changed, or he put the symbol of the lion first because it is not on account of the Nativity or of the Passion that people have believed in Christ, but on account of the Resurrection, which is symbolized by the lion. Finally, since he began with the human generation, [Sc. of Jesus. Matt. 1:1 et seq.] Matthew is appropriately represented by the man; since he began with the cry in the desert, [Mark 1:3] Mark is appropriately represented by the lion; since he started with a sacrifice, [Luke 1:8] Luke is well represented by the calf; and John, who began with the divinity, [John 1:1 et seq.] is fittingly represented by the eagle. All this can also refer to Christ and all his limbs. However, for brevity's sake, let us content ourselves with what we have said here.