Saying, Let us alone; what have we to do with thee, thou Jesus of Nazareth? art thou come to destroy us? I know thee who thou art, the Holy One of God. What have we to do with thee - Or, What is it to us and to thee? or, What business hast thou with us? That this is the meaning of the original, τι ἡμιν και σοι, Kypke has sufficiently shown. There is a phrase exactly like it in 2 Samuel 16:10. What have I to do with you, ye sons of Zeruiah? מה לי ולכם בני צרויה ma li v'lacem beney Tseruiah, What business have ye with me, or, Why do ye trouble me, ye sons of Tseruiah? The Septuagint translate the Hebrew just as the evangelist does here, τι εμοι και ὑμιν; it is the same idiom in both places, as there can be no doubt that the demoniac spoke in Hebrew, or in the Chaldeo-Syriac dialect of that language, which was then common in Judea. See on Matthew 8:29 (note).
Art thou come to destroy us? - We may suppose this spirit to have felt and spoken thus: "Is this the time of which it hath been predicted, that in it the Messiah should destroy all that power which we have usurped and exercised over the bodies and souls of men? Alas! it is so. I now plainly see who thou art - the Holy One of God, who art come to destroy unholiness, in which we have our residence, and through which we have our reign in the souls of men." An unholy spirit is the only place where Satan can have his full operation, and show forth the plenitude of his destroying power.