Guide for the Perplexed, by Moses Maimonides, Friedländer tr. [1904], at sacred-texts.com
IT is well known that there are men whose face is like that of other animals thus the face of some person is like that of a lion, that of another person like that of an ox, and so on: and man's face is described according as the form of his face resembles the form of the face of other animals. By the expressions, "the face of an ox," "the face of a lion," "the face of an eagle" (Ezek, i. 10), the prophet describes a human face inclining towards the forms of these various species. This interpretation can be supported by two proofs. First, the prophet says of the Ḥayyot in general that" their appearance is this, they have the form of man" (ver. 5), and then in describing each of the Ḥayyot he attributes to them the face of a man, that of an ox, that of a lion, and that of an eagle. Secondly, in the second description of the Chariot, which is intended as a supplement to the first, the prophet says, Each hath four faces; the one is the face of a cherub, the second a man's face, the third a lion's face, and the fourth that of an eagle (ibid. x. W. He thus clearly indicates that the terms "the face of an ox" and "the face of a cherub" are identical. But cherub designates "a youth." By analogy we explain the two other terms--"the face of a lion" and "the face of an eagle" in the same manner. "The face of the ox" has been singled out on account of the etymology of the Hebrew term shor (ox), as has been indicated by me. It is impossible to assume that this second description refers to the perception of another prophetic vision, because it concludes thus: "This is the Ḥayyah which I saw at the river Chebar" (ibid. ver. 15). What we intended to explain is now clear.