The prophet Ezekiel, by the river Chebar, saw the heavens open and a chariot descend. Beneath it were four living creatures, and each creature had four faces. As for the likeness of their faces, they four had the face of a man, and the face of a lion on the right side; and they four had the face of an ox on the left side; they four also had the face of an eagle (Ezekiel 1:10).
The Midrash Shemot (chapter 23) asks: why these four? Because they are the kings of their domains. The man is the excellence of all created beings. The eagle is the excellence of the birds. The ox is the excellence of all domestic cattle. And the lion is the excellence of the wild beasts.
Each is the highest of its kind. And all four are harnessed, fixed under the chariot of God.
Why? The midrash answers bluntly: so that they would not exalt themselves. So that each could feel, always, the weight of the chariot above them. Even the king of beasts must know there is a kingdom of Heaven over him. This, says the midrash, is the meaning of Ecclesiastes 5:8: He that is higher than the highest regardeth; and there be higher than they.
Every creature that reaches the top of its order discovers, looking up, that it is still carrying a chariot. The highest of the highest are still servants. Humility is not a weakness; it is the posture of the ones who actually know what they are under.