Because they said: He hath an unclean spirit.

“(Serm. 71, 12, 21) Or else impenitence itself is the blasphemy against the Holy Ghost which hath no remission. For either in his thought or by his tongue, he speaks a word against the Holy Ghost the forgiver of sins, who treasures up for himself an impenitent heart. But he subjoins, Because they said, He hath an unclean spirit, that he might shew that His reason for saying it, was their declaring that He cast out a devil by Beelzebub, not because there is a blasphemy, which cannot be remitted since even this might be remitted through a right repentance: but the cause why this sentence was put forth by the Lord, after mentioning the unclean spirit, (who as our Lord shews was divided against himself,) was, that the Holy Ghost even makes those whom He brings together undivided, by His remitting those sins, which divided them from Himself, which gift of remission is resisted by no one, but him who has the hardness of an impenitent heart. For in another place, the Jews said of the Lord, that He had a devil, (John 7:20.) without however His saying any thing there about the blasphemy against the Spirit; and the reason is, that they did not there cast in His teeth the unclean spirit, in such a way, that that spirit could by their own words be shewn to be divided against Himself, as Beelzebub was here shewn to be, by their saying, that it might be he who cast out devilso.”

“(Vict. Ant. e Cat. in Marc.) He says indeed, that blasphemy concerning Himself was pardonable, because He then seemed to be a man despised and of the most lowly birth, but, that contumely against God has no remission. Now blasphemy against the Holy Ghost is against God, for the operation of the Holy Ghost is the kingdom of God; and for this reason, He says, that blasphemy against the Holy Ghost cannot be remitted. Instead, however, of what is here added, But will be in danger of eternal damnation, another Evangelist says, Neither in this world, nor in the world to come. By which is understood, the judgment which is according to the law, and that which is to come. For the law orders one who blasphemes God to be slain, and in the judgment of the second law he has no remission. nHowever, he who is baptized is taken out of this world; but the Jews were ignorant of the remission which takes place in baptism. He therefore who refers to the devil miracles, and the casting out of devils which belong to the Holy Ghost alone, has no room left him for remission of his blasphemy. Neither does it appear that such a blasphemy as this is remitted, since it is against the Holy Ghost. Wherefore he adds, explaining it, Because they said, He hath an unclean spirit.”