Matthew 17:21

21. This kind The word kind may mean the entire species of evil spirits, and then our Lord would mean to say that to cast out evil spirits requires prayer and fasting. Or it may mean that this special kind of evil spirits which infested this child requires special faith, or special effort to give effect to that faith. The latter is the more obvious, and therefore the more probable meaning. That there are various grades of spirits of evil is not improbable in itself; and the idea is sustained by many proofs. The very fact that Beelzebub is prince of devils, shows this. Mark, by his glowing description of the fierceness both of this demon and of the demons at Gadara, evidently means to convey the idea that there are demons of more than ordinary fierceness. Matthew tells us (Matthew 12:45) of one who took “seven other spirits more wicked than himself.” And Paul (Ephesians 6:12) evidently describes divers orders of evil. We may safely conclude, therefore, that our Lord meant to say that this sort of demon required more than ordinary spiritual vigour to expel him. And here we have a solemn intimation that we have all, nigh unto us, spiritual foes of various power, whose force can be overcome by the vigorous use of the means of training our spiritual strength.