And no marvel; for Satan himself is transformed into an angel of light.
All Commentaries on 2 Corinthians 11:14 Go To 2 Corinthians 11
Augustine of Hippo
AD 430
As for the power of darkness, what is it but the power of the devil and his angels, who, after being angels of light, did not use their free will to stand in the truth but by falling from it became darkness? I am not teaching you this; I am advising you to call to mind what you know. So, the human race became subject to this power of darkness by the fall of the first man who was induced by that power to commit sin, and in him we have all fallen. Letter , To Vitalis.