Origen

Or; The scandals that are to come are the Angels of Satan. But do not look that these offences should shew themselves in a substantial or natural shape, for in some the freedom of the will has been the origin of offence, not liking to undergo toil for virtue’s sake. But there cannot be real good, without the opposition of evil. It must needs be then that offences come, as it must needs be that we encounter the evil assaults of spiritual powers; whose hatred is the more stirred up, as Christ’s word invading men drives out the evil influences from them. And they seek instruments by whom the offences may the rather work; and to such instruments is more woe; for him who gives, it shall be worse than for him who takes, the offence, as it follows, But woe unto that man by whom the offence cometh.