Ezekiel 1:23

And under the firmament were their wings straight, raised aloft as they moved forward in an erect position, the one toward the other; every one had two, which covered on this side, when let down, and every one had two, which covered on that side, their bodies. "The tips of the wings (of the pair of wings serving for flight) reach along to the vault. For support they are adapted, and particularly for this reason that the wings, make a loud noise and are therefore in free motion; and further, because, upon occasion they are let down. The wheels also do not support the chariot. The local proximity seems only to indicate the connection between the several provinces of creation; it is meant to represent the creation as a united whole. " (Hengstenberg)