John Chrysostom
The word Spirit is applied to an Angel, the air, the soul, and even the Holy Ghost. Lest therefore by the sameness of the name we should fall into error, he adds, unclean. And he is called unclean on account of his impiousness and far removal from God, and because he employs himself in all unclean and wicked works.
Or else the devil so speaks, as if he said, ‘by taking away uncleanness, and giving to the souls of men divine knowledge, Thou allowest us no place in men.’
As if he said, Methinks that Thou art come; for he had not a firm and certain knowledge of the coming of God. But he calls Him holy not as one of many, for every prophet was also holy, but he proclaims that He was the One holy; by the article in Greek he shews Him to be the One, but by his fear he shews Him to be Lord of all.
Further, the Truth did not wish to have the witness of unclean spirits; wherefore there follows, And Jesus threatened him, saying, &c. Whence a healthful precept is given to us; let us not believe devils, howsoever they may proclaim the truth. It goes on, And the unclean spirit tearing him, &c. For, because the man spoke as one in his senses and uttered his words with discretion, lest it should be thought that he put together his words not from the devil but out of his own heart, He permitted the man to be torn by the devil, that He might shew that it was the devil who spoke.