Guide for the Perplexed, by Moses Maimonides, Friedländer tr. [1904], at sacred-texts.com
WHEN Ezekiel recalled to memory the form of the Chariot, which he described in the beginning of the book, the same vision presented itself to him a second time; in this vision he was borne to Jerusalem. He explains in describing it things which have not been made clear at first, e.g., he substitutes the term "cherubim" for Ḥayyot, whereby he expresses that the
[paragraph continues] Ḥayyot of the first vision are likewise angels like the cherubim. He says, therefore: "Where the cherubims went, the Ofannim went by them: and when the cherubims lifted up their wings to mount up from the earth, the same Ofannim also turned not from beside them" (x. 16). By these words he shows how closely connected the two motions are [viz., that of the Ḥayyot and that of the Ofannim]. The prophet adds, "This is the Hayyah that I saw under the God of Israel by the river of Chebar: and I knew that they were cherubims" (ver. 20). He thus describes the same forms and the same motions, and states that the Ḥayyot and the cherubim are identical. A second point is then made clear in this second description, namely, that the Ofannim are spherical; for the prophet says, "As for the Ofannim, it was cried unto them in my hearing, O sphere" (ver. 13). A third point concerning the Ofannim is illustrated here in the following words: "To the place whither the head looked they followed it: they turned not as they went" (ver. 11). The motion of the Ofannim is thus described as involuntary, and directed "to the place whither the head looketh"; and of this it is stated that it moves "whither the spirit is to go" (i. 20). A fourth point is added concerning the Ofannim, namely, "And the Ofannim were full of eyes round about, even the Ofannim that they four had" (x. 12). This has not been mentioned before. In this second description there are further mentioned" their flesh, and their backs, and their hands, and their wings" (ibid.), whilst in the first account none of these is mentioned: and it is only stated that they are bodies. Though they are endowed in the second account with flesh, hands, and wings, no form is given to them. In the second account each Ofan is attributed to a cherub, "one Ofan by one cherub, and another Ofan by another cherub." The four Ḥayyot are then described as one Hayyah on account of their interjoining: "This is the Ḥayyah that I saw under the God of Israel by the river of Chebar" (ver. 20). Also the Ofannim, though being four in number, as has been mentioned, are called "one ofan upon the earth" (ver. 15), because they interjoin, and "they four have one likeness" (ver. 16). This is the additional explanation which the second vision gives of the form of the Ḥayyot and the Ofannim.