"The unclean spirit, banished by baptism, and not caring to be homeless, seeks rest, walking here and there; finding no home, he returns to the house from whence he came out, for he is shameless. If he finds that Christ is held by the attention and the love of the baptized man, and is established and dwelling in the place from whence he had been cast out, that is in the heart, he fails to enter and again turns away. But if he finds his former place empty, occupied by no one, through absence of attention towards God and memory of Him, he enters hastily, with greater malice than before. And the last state of that man is worse than the first."

Lorenzo Scupoli, quoting St. Gregory the Theologian

Gregory the Theologian