“And Jesus said unto them, Because of your unbelief: for verily I say unto you, If ye have faith as a grain of mustard seed, ye shall say unto this mountain, Remove hence to yonder place; and it shall remove; and nothing shall be impossible unto you.”
King James Version (KJV)
17:20 Because of your unbelief - Because in this particular they had not faith. If ye have faith as a grain of mustard seed - That is, the least measure of it. But it is certain, the faith which is here spoken of does not always imply saving faith. Many have had it who thereby cast out devils, and yet will at last have their portion with them. It is only a supernatural persuasion given a man, that God will work thus 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. To remove mountains was a proverbial phrase among the Jews, and is still retained in their writings, to express a thing which is very difficult, and to appearance impossible. #Matt 21:21|; Luke 17:6.
Mt 17:20 This mountain. Lofty Hermon, in plain sight. Nothing shall be impossible unto you. Upon the condition of perfect faith. Compare Heb 11:1-40. Faith in Christ, faith exercised in fasting and prayer, are the conditions of power.