Note 2 at Mt. 17:20: The disciples' unbelief in this instance was not a disbelief that God's power could produce deliverance (see note 1 at Lk. 9:41, p. 211) but rather a "natural" kind of unbelief that came from a hardened heart (see note 10 at Mk. 6:52, p. 179) that was more sensitive to what it saw (Mk. 9:20) than to what it believed.

Note 3 at Mt. 17:20: Jesus did not say that the reason these disciples could not cast this demon out was because they didn't have faith but because they had unbelief. On the contrary, Jesus states that a very small amount of faith (a "mustard seed") is sufficient to remove a mountain if no unbelief is present to hinder it.

Most people have the concept that you either have faith or unbelief but that you can't have both at the same time. However, Jesus told Jairus to "believe only" (Lk. 8:50) implying that faith and fear can operate in us at the same time. This is also the reason James tells us not to be double-minded (Jas. 1:5-8). We can be thinking faith and yet have thoughts of unbelief at the same time.

As explained in note 1 at Matthew 17:19, page 210, these disciples did have faith to cast this demon out, and they exercised that faith, but didn't see the same results that they had seen before. This is why they were concerned and asked Jesus what the problem was. They wouldn't have asked if they had not believed. They did have faith--the same faith that had effected many other deliverances. The problem wasn't their faith but rather their unbelief.

Every believer has been given "the measure of faith" but our unbelief negates it. It's like hooking a team of horses up to a heavy weight and having them pull it. The weight will move. But if you hook an equal team of horses up to the same weight and have them pull in the opposite direction at the same time, although great force may be exerted, the weight won't move. Likewise, unbelief counterbalances our faith. If we will just remove the unbelief, a mustard seed amount of faith will be sufficient to move our problems.

Instead of trying to build huge amounts of faith to overcome our fears and unbelief, a simpler method is to remove our fears by cutting off their source; then our simple "child-like" faith that remains will do the job. It doesn't take big faith--just pure faith.

Those who tolerate high levels of unbelief in their lives will never be able to build their faith big enough to overcome unbelief's negative force. The only way they can receive is to get others to mix their faith with them or draw on one of the supernatural ministry gifts in someone else, such as the gift of faith (1 Cor. 12:9). God's best is for us to receive directly from Him. We will only be successful at that when we not only build our faith but also destroy our doubts. (See note 10 on a hardened heart at Mk. 6:52, p. 179.)