Matthew 17:20 - Coke's Commentary on the Holy Bible

Because of your unbelief— When the disciples were come with our Lord, they askedhim the reason why they could not cast out that particular demon; to which he replies, because of your unbelief.—"Knowing that you doubted whether I could enable you to cast out this demon, I ordered it so, that he would not go out at your command, for a reproach of the weakness of your faith." We may observe that the disciples had attempted to cast him out. To encourage them, our Lord describes to them the efficacy of the faith of miracles; If ye have faith as a grain of mustard-seed, &c. If you have but the least degree of the faith of miracles, you may say to the vast mountain whence we just now came down, Move thyself, and go to some other place, and it shall obey you. Ye shall by that faith be able to accomplish the most difficult things, in all cases where the glory of God and the good of his church are concerned. It is certain that the faith which is here spoken of may subsist without saving faith: Judas had it, and so had many, who thereby cast out devils, and yet will at last have their portion with them. It is only a supernatural persuasion given to a man that God will work miracles by him at that hour. Now, though I have all this faith so as to remove mountains, yet if I have not the faith which worketh by love, I am nothing. Not only the persons on whom the power of working miracles was bestowed, were obliged to have faith likewise, in order to the exercise of that power; but it was a different kind of faith from that which was necessary in the subject of the miracles. For it consisted, first, in a just and high notion of the divine power, by which the miracle was to be effected: secondly, as we observed, in a firm persuasion that the miracle was to be wrought at that particular time. Now this persuasion was to spring from a two-fold source: 1. A consciousness of the power which Christ had conferred on them when he ordained them his Apostles: 2. It was to arise from a sensible impression made upon their minds by the Spirit of God, signifying to them that a miracle was to be performed at that time. Accordingly, the Apostles, and such of the first Christians as were afterwards honoured with the power of miracles, never attempted to exerciseit without feeling an impression of this kind; as is plain from St. Paul's leaving Trophimus at Miletum, sick.—Wherefore as the nine had, in all probability, attempted to cure the youth spoken of in this account, and had made the attempt with some degree of doubtfulness, it is no wonder that they were unsuccessful. To remove mountains is a proverbial expression, which signifies the doing of any thing seemingly impossible, as we may learn from Zechariah 4:7. When the Jews had a mind to extol any of their doctors, they were used to say of him that he plucked up mountains by the roots. In this description of the efficacy of faith, there is abeautiful contrast between the smallness of a grain of mustard seed, to which their faith is compared, and the vast size of the mountain that was to be removed thereby. Dr. Heylin finely remarks, "All inanimate nature is passive to Deity, and therefore infallibly executes what it is designed for. When faith is consummate in the human nature, that becomes alike susceptible of the divine energy."