John Calvin Commentary Ezekiel 10:21

"Every one had four faces, and every one four wings; and the likeness of the hands of a man was under their wings." — Ezekiel 10:21 (ASV)

The Prophet appears to dwell on points that are certainly not doubtful. He has already spoken of the four heads; why, then, does he repeat it?

He did so because he was dealing with a dull and perverse people. These people were also slow to receive the Prophet’s doctrine. Moreover, they added this vice, worse than all the others: a constant and open endeavor to detract from the authority of all the Prophets.

For this reason, the Prophet states that there were four heads and four wings to each living creature, so that the Jews would not scoffingly deride it as an empty specter and delusion of the Prophet, as if he thought he saw what had no existence. For this reason also, he repeatedly emphasizes what would have been sufficiently clear by itself, had the Jews been teachable and obedient.