When the unclean spirit is gone out of a man. — The parable comes in abruptly, possibly because here, as elsewhere, we have a part and not the whole of a discourse, striking passages noted and put together, now in this order, now in that, while the links that joined them are missing. The inner connection of thought is, however, clear enough. How was it, it might be asked, that Israel had sunk to such a depth of evil? and the answer was found in the similitude which thus opens. The phenomena which furnish the comparison were probably familiar enough. So far as possession was identical in its phenomena, wholly or in part, with insanity, there might be sudden and violent relapses after intervals of calmness and apparent cure. The spirit of the man, under the influence of exorcisms, or prayers, or the sympathy of friends, might assert its freedom for a time, and then yield again to the oppressor. In the history of such a demoniac, which our Lord narrates in the language of the popular belief, He sees a parable of the history of the Jewish people.
Walketh through dry places. — The description reflects the popular idea that the parched deserts of Syria and Arabia and Egypt were haunted by demons, who thence came to invade the bodies and the souls of men. So in the book of Tobit (Tob. 8:3), the demon Asmodeus flees to the upper parts of Egypt.