Tertullian

“ Never did any angel descend for the purpose of being crucified, of tasting death, and of rising again from the dead. Now, since there never was such a reason for angels becoming embodied, you have the cause why they assumed flesh without undergoing birth. They had not come to die, therefore they also (came not) to be born. Christ, however, having been sent to die, had necessarily to be also born, that He might be capable of death; for nothing is in the habit of dying but that which is born. Between nativity and mortality there is a mutual contrast. ”

“ They, who were able to convert themselves into flesh have it in their power to convert nothing itself into flesh. It is a greater thing to change a nature than to make matter. But even if it were necessary to suppose that angels derived their flesh from some material substance, it is surely more credible that it was from some earthly matter than from any kind of celestial substances, since it was composed of so palpably terrene a quality that it fed on earthly ailments. ”

“ It is plain that the angels bore a flesh which was not naturally their own; their nature being of a spiritual substance, although in some sense peculiar to themselves, corporeal; and yet they could be transfigured into human shape, and for the time be able to appear and have intercourse with men. Since, therefore, it has not been told us whence they obtained their flesh, it remains for us not to doubt in our minds that a property of angelic power is this, to assume to themselves bodily shape out of no material substance. ”