Matthew 17:19

Observe here, How ashamed the disciples were of this open rebuke given them by their Master; they privately ask him the case of their ill success, Why they could not cast out Satan, according to the power promised them to work miracles? Our Saviour tells them, that their power to work this miracle now failed them for. double reason.

1. For their unbelief, by which we are to understand the weakness of their faith, not the total want of faith.

2. Because they neglected the special means appointed by God, in order to that end, to wit, fasting and prayer: that is. fervour of devotion, joined with faith and fasting.

Thence learn, That fasting and prayer are two especial means of Christ's appointment, for enabling us victoriously to overcome Satan, and cast him out of ourselves and others. We must set an edge upon our faith by prayer, and upon our prayer by fasting.

Question. But what are we to understand by faith as. grain of mustard-seed?

Answer. 1. Some do thereby understand. faith that groweth and increaseth as. grain of mustard-seed, or. faith as strong and active in heart as mustard-seed is on the palate. And by removing mountains, understand the performing things that are most difficult; as if Christ had said, Did your faith increase as. grain of mustard-seed grows, it would enable you to surmount all difficulties whatsoever.

2. Others by faith as. grain of mustard-seed, understand, the least degree of sincere faith on God, it being. proverbial speech among the Jews, used pro reminima, for the least thing; as if Christ had said, "Had you the least measure of that faith which cast out fear and doubting of success in the discharge of your office, you might perform things most difficult, and even this faith in its effects would be mighty." Dr. Whitby.