Ezekiel 1:18

It hath been said by God that their [four] sides were "living animals" [which] were "full of eyes as they turned round." And by this word He hath taught us that the whole of the spiritual nature can see, and that all of it can …

(Verse 15 and following) And as I looked at the animals, a wheel appeared on the earth beside the animals, having four faces. And the appearance of the wheels and their work was like the vision of the sea, and the four of them had the same likeness, and their appearance and work was as a wheel within a wheel. They went in the four directions, and they did not turn as they walked. The wheels also had a height and a terrifying appearance, and the whole body was full of eyes all around the four of them. LXX: And I saw, and behold, a wheel was following animals four over the earth. And the appearance of the wheels and their construction was like the color of tarshish. And their appearance was in four: and their work was as it were a wheel within a wheel. They walked in their four parts, and did not turn back when they walked. And their backs and their height were to them. And I saw them, and their backs were full of eyes all around the four. Up to this point, the picture describes the four living creatures that had four faces, following the spirits and the cloud that was in the midst of the spirit, now the individual wheels are mentioned for each animal, which were not attached to the animals but followed them. Or a wheel appeared upon the Earth, which, divided into four, had as many faces as the number of animals that followed. And such was the similarity of the four wheels to the four following animals, that one wheel was truly believed. And their work and creation was like the vision of tharsis, which we turn into the sea. The eagle placed the hyacinth; which stone resembles the sky. And their appearance was like one wheel in another, so that you would not believe it was one wheel, but rather one wheel joined to another. They were moving in four directions, and they were not being dragged or turned back. […]

As you know, dearest brothers, it is the custom of prophecy to look now at this, now at that, and suddenly to turn words from one thing to another, as the Psalmist, when speaking of the Lord, said: "God is a just judge, strong and patient; is He angry every day? Unless you are converted, He has brandished His sword, He has bent His bow and made it ready; and in it He has prepared instruments of death, He has made His arrows for those who burn"; suddenly he adds: "He conceived sorrow and brought forth iniquity; he opened a pit and dug it out, and fell into the hole he made." Behold, when he was narrating the Lord's justice, as if without changing his voice, he suddenly introduced the guilt of the sinner. Let it suffice that I have said this one example by way of illustration, because whoever has practice in reading the prophets knows how frequently they do this. Hence now the prophet Ezekiel, when he was speaking about the wheels, added: "And the whole body was full of eyes around the four of them." For he who said "of them" (masculine) rather than "of them" (feminine) clearly indicates that his speech suddenly returned from the wheels to the living creatures. By these, as was said before, all perfect persons are designated. Therefore the bodies of the living creatures are described as full of eyes, because the action of the saints is circumspect on every side, desirously providing for good things, skillfully guarding against evil things. And this is more laborious where the mind of the saints vigilantly watches lest evils hide themselves before their eyes under the appearance of good things. Therefore the life of the saints is circumspect, lest it be so free as to be proud, because often pride exceeds in words, and desires to appear as the freedom of purity. […]

What is it that in the words of Sacred Scripture these three things are said to be present, so that they are mentioned as having stature, height, and a horrible appearance, that is, a terrible one? We must greatly inquire what is called the stature of divine Scripture, what is its height, what is its horrible appearance. Therefore it must be known that to stand corresponds to the life of one who works well. Hence it is said through Paul: Let him who stands take heed lest he fall. He who also says to his disciples: So stand in the Lord, beloved. And the prophet, who saw himself standing before the Lord in life and conduct, said: The Lord lives, in whose sight I stand. Height, however, is the promise of the heavenly kingdom. Which is reached when all corruption of mortal life is now subdued. The horrible appearance, however, is the terror of hell, which tortures the reprobate without end, and always preserves them in torment. Therefore stature is in the rectitude of precept, height in the loftiness of the heavenly promise, and horrible appearance in the threats and terrors of the punishment that follows. Sacred Scripture therefore has stature, because it directs conduct toward standing, so that the minds of hearers may not be bent toward earthly desire. It has height, because it promises the joys of eternal life in the heavenly homeland. It also has a horrible appearance, because it threatens all the reprobate with the punishments of hell. Therefore it shows its stature in the building of conduct, it shows its height in the promise of rewards, it shows its horrible appearance in the terrors of punishments. For it is upright in precepts, lofty in promises, horrible in threats. It has stature when it says through the prophet: Cease to do evil, learn to do good, seek judgment, relieve the oppressed, judge the orphan, defend the widow. […]

Those who are over others are to be warned that through prudence they should attain watchful eyes within and round about and strive to become living creatures of heaven. For the living creatures of heaven are described as full of eyes round about and within. So it is fitting that those who are over others should have eyes within and round about, so that in striving to please the inward judge and in serving outwardly as examples of life, they may detect the things that should be corrected in others.