This also is a part of the teaching of the Church, that there are certain angels of God, and certain good influences, which are His servants in accomplishing the salvation of men. When these, however, were created, or of what nature they are, or how they exist, is not clearly stated. Regarding the sun, moon, and stars, whether they are living beings or without life, there is no distinct deliverance.
Origen
On First Principles, Book I
Preface
Regarding the devil and his angels, and the opposing influences, the teaching of the Church has laid down that these beings exist indeed; but what they are, or how they exist, it has not explained with sufficient clearness. This opinion, however, is held by most, that the devil was an angel, and that, having become an apostate, he induced as many of the angels as possible to fall away with himself, and these up to the present time are called his angels.
Origen
On First Principles, Book I
Preface
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.
Tertullian
On the Flesh of Christ
Chapter VI
You have sometimes read and believed that the Creator’s angels have been changed into human form, and have even borne about so veritable a body, that Abraham even washed their feet, and Lot was rescued from the Sodomites by their hands; an angel, moreover, wrestled with a man so strenuously with his body, that the latter desired to be let loose, so tightly was he held. Has it, then, been permitted to angels, which are inferior to God, after they have been changed into human bodily form, nevertheless to remain angels? and will you deprive God, their superior, of this faculty, as if Christ could not continue to be God, after His real assumption of the nature of man? Or else, did those angels appear as phantoms of flesh? You will not, however, have the courage to say this; for if it be so held in your belief, that the Creator’s angels are in the same condition as Christ, then Christ will belong to the same God as those angels do, who are like Christ in their condition. If you had not purposely rejected in some instances, and corrupted in others, the Scriptures which are opposed to your opinion…
Tertullian
On the Flesh of Christ
Chapter III