Matthew 8:31 - Ellicott's Commentary On The Whole Bible

So the devils besought him. — As St. Mark gives the words, “that He should not send them out of the country,” or district, in which they were; as in St. Luke’s report, “that He would not command them to go out into the deep,” i.e., the abyss, the “bottomless pit” of Revelation 9:1-2; Revelation 9:11. The words of the man are as those of the demons with whom he identifies himself. He shrinks from the thought of wandering in dry places, “seeking rest, and finding none” (Matthew 12:43), or being compelled to flee, like Asmodeus, into “the utmost parts of Egypt” (Tob. 8:3), or, worst fate of all, to be sent into the “abyss,” which was the ultimate doom of evil. And so he, as one with them, suggests another alternative: “If Thou cast us out, send us into the herd of swine. If the power to terrify and disturb men is taken from us, let us, at least, retain the power to destroy brutes.”