Adam Clarke on Ezekiel 1:6

Every one had four faces - There were four several figures of these living creatures, and each of these figures had four distinct faces: but as the face of the man was that which was presented to the prophet's view, so that he saw it more plainly than any of the others; hence it is said, Eze 1:5, that each of these figures had the likeness of a man; and the whole of this compound image bore a general resemblance to the human figure.