Ezekiel 1:7

The four animals that bore the chariot were a type of the leading characteristics of the soul. For as the eagle rules over all the other birds and the lion is king of the wild beasts and the bull over the tamed animals and humanity …

After this description of the prophet, we still cannot comprehend as we read. But if we cannot comprehend the throne that he has described, how will we be able to comprehend him who sits on it, the invisible and ineffable God? It is impossible to examine closely the nature of God, but for his works, which we see, we can offer him praise and glory.

After I wrote the letter, I remembered what is written in Ezekiel, which he showed as an example of perfection. He saw an animal above the river Chebar that had four faces and four feet and four wings. The face of the cherub is when …

What is designated by feet if not the steps of actions? Therefore the feet of the four living creatures are described as being straight, because the works of the holy evangelists and of all the perfect are not twisted to follow iniquity. But those do not have straight feet who are bent back to the evils of the world which they had abandoned. Of whom it is written: "The dog returned to his own vomit, and the sow that was washed to her wallowing in the mire." The distinguished teacher grieved over certain ones because they had twisted the straightness of their feet backward, to whom he said by way of rebuke: "How do you turn again to the weak and beggarly elements, which you desire to serve again? You observe days, and months, and seasons, and years. I fear for you, lest perhaps I have labored among you in vain." He who admonishes others, saying: "Therefore lift up the hands that hang down, and the weakened knees, and make straight steps with your feet." But in order that gravity of life, fortitude, and discretion might be shown in these same holy preachers, it is rightly added: "The sole of their foot was like the sole of a calf's foot." For the holy preachers are designated by the name of oxen, as Paul the Apostle teaches, explaining the testimony of the law: "You shall not muzzle the ox that treads out the grain." In the holy preachers, therefore, the sole of the foot is that of a calf, namely proceeding with maturity, and strong, and divided, because each preacher has both reverence in maturity, and strength in work, and division of the hoof in discernment. For his preaching is not easily received if he appears to be frivolous in his conduct. And there will be no display of maturity if strength of work is not present against all adversities. Moreover, the strength of work itself loses the merit of virtue if it is not discerning in understanding. […]

The sole of their feet was like that of a calf's foot, which divides the hoof and is therefore clean: as it were the sole of a round foot (as the Chaldee words it); they were ready for motion any way. Their feet were winged (so the LXX.); they went so swiftly that it was as if they flew.