30. The Chayos and Ofanim
The Rambam goes on to explain the vision of the angels in Ezekiel chapter 1. [III, 2] Each angel has the four faces we discussed in our previous section, four wings and two hands. Overall, however, their appearance is human, as per Ezekiel 1:5, "they had the form of a man."
The legs of the angels are described as "straight legs" (Ezekiel 1:7), meaning that their legs have no joints. The Sages understood from this that angels do not sit, and it is this straight-legged physiology that we emulate while reciting Kedusha. While the angels have hands like humans, their feet are rounded (ibid.). The four aspects of an angel are all connected below, without any space between them (verse 9), but their wings and faces are separated above (verse 11).
The angels are transparent, the color of "burnished brass" (verse 7), but glowing "like burning coals" (verse 13). They move uniformly, never deviating, as per verse 17, "they did not turn as they went." They also move very quickly, "running back and forth, like lightning" (verse 14). We are told that each angel moves in the direction of its face (verse 9) - but each angel has four faces! It would therefore appear that each aspect of an angel moves in a different direction.
The angels move to and fro, but not of their own accords. Rather, they move wherever God wills them to go (not unlike the lightning they so resemble). We see this in verse 20, "wherever the spirit (of God) willed them to go, there they went." The Hebrew word "ruach" in this verse does not mean the wind, but rather the Divine spirit. (This is also how this verse is understood in the Targum of Yonasan ben Uziel.)
The angels we've been describing so far are of an order called "Chayos" ("living things"). From here, Ezekiel goes on to describe another order of angels, called "Ofanim" ("wheels"). The Ofanim are the color of beryl (a shade of green - see verse 16) and are covered with eyes (or, possibly, different colors - verse 18). One part of them touches the Chayos, while another part touches the ground (verse 15). The Ofanim were somehow interconnected, described as "a wheel within a wheel" (verse 16).
The Ofanim move straight, without deviation (verse 17: "they did not turn as they went"). They do not have their own means of propulsion; rather, they are set in motion by the Chayos, as we see in verse 19 ("when the Chayos went, the Ofanim went alongside them...") and in verse 21 ("when these went, those went, and when these stood, those stood..."). The reason for this is given in verse 20: "the spirit of the Chaya was in the Ofanim." We therefore see that wherever God wills, that is where the Chayos go. When the Chayos go somewhere, the Ofanim travel with them.
After describing these two classes of angels, Ezekiel describes a firmament that he saw above them and, above that, something that resembled a throne with a person on it. This is the entirety of what Ezekiel saw in his first vision.