Spiritists of our day accept every manifestation from the spiritual world as though sent by God, and immediately they boast that God has been “revealed” to them. I knew an eighty year old monk whom everyone respected as a great spiritual director. To my question: “Have you ever in your life seen anything from the spiritual world?”, the monk answered me, “No, never, praise be to God’s Mercy.” Seeing that I was astonished at this, he said, “I have constantly prayed to God that nothing appear to me, so that, by chance, I would not succumb to pride and receive a fallen devil as an angel. Thus far, God has heard my prayers.” This recorded example shows how humble and cautious the elders were. The devil, clothed in the light of an angel, appeared to a certain monk and said to him: “I am the Archangel Gabriel and I am sent to you.” To that, the brother responded, “Think! Were you not sent to someone else, for I am not worthy to see an angel?” The devil instantly became invisible and vanished.
h/t "Christ is in Our Midst"