Gregory the Great
Catena Aurea · Matthäusevangelium 12
When the unclean spirit is gone out of a man, he walketh through dry places, seeking rest, and findeth none. Then he saith, I will return into my house from whence I came out; and when he is come, he findeth it empty, swept, and garnished. Then goeth he, and taketh with himself seven other spirits more wicked than himself, and they enter in and dwell there: and the last state of that man is worse than the first. Even so shall it be also unto this wicked generation.
(Mor. xxxiii. 3.) The dry places where no water is are the hearts of the righteous, which by the power of discipline are dried from all humours of carnal lust. The wet places are the minds of worldly men, which the humour of carnal lust fills, and makes watery; in such the Devil imprints his footsteps the more deeply, inasmuch as in his wanderings he comes down upon such hearts as upon low and marshy ground.