A couple days ago I posted D.A. Carson’s commentary on the incident in Matthew 17 when Jesus told told his followers they had “little” faith. “Probably,” Carson notes, this word “does not refer so much to the littleness of their faith as to its poverty. Little faith, like a little mustard seed, can be effectual; poor faith, like that of the disciples’ here, is ineffectual.”
A person who commented asked for further explanation of this idea. So, here’s the rest of what Carson wrote:
Despite the etymology of the word [“little”], it probably does not refer so much to the littleness of their faith as to its poverty. Little faith, like that of the disciples’ here, is ineffectual. The noun occurs only here in Matthew, but the cognate adjective occurs at 6:30; 8:26; 14:31; 16:8, and always refers to disciples.
Removal of mountains was proverbial for overcoming great difficulties (Isa 40:4; 49:11; 54:10; Mt 21:21-22; Mk 11:23; Lk 17:6; 1 Cor 13:2). Nothing would be impossible for them—a promise that, like its analogue in Philippians 4:13, is limited by context, not by unbelief. Here it refers to the accomplishment of the works of the kingdom, for which they had been given authority.
Jesus’ answer in Matthew is not the same as the one in Mark 9:29 (“This kind can come out only by prayer”), but if the comment [above] on oligopetia ([the Greek word that means] “poverty of faith”) is correct, then at least the two answers are complementary, each shedding light on the other.
At a superficial level, the disciples did have faith. They expected to be able to exorcise the demon. They had long been successful in this work, and now they are surprised by their failure. But their faith is poor and shoddy. They are treating the authority given them (10:1,8) like a gift of magic, a bestowed power that works ex opera operato.
In Mark, Jesus tells them that this case requires prayer—not a form or an approved rite, but an entire life bathed in prayer and its concomitant faith. In Matthew, Jesus tells his disciples that what they need is not giant faith (tiny faith will do) but true faith—faith that, out of a deep personal trust, expects God to work.
So maybe the idea here is that Jesus called the disciples faith “little” because it was of poor quality, because they thought that trusting God was some kind of magic they could wield whenever they wanted. But this incident shows that faith, and the miraculous power of God, do not work like that. This needs to be said today, right? There are whole groups of Christians in America who teach that true faith operates exactly this way—that if you have faith you can just speak to things and change circumstances. And they might even read this passage to mean that Jesus was rebuking the disciples for not having that kind of power-speaking faith. But actually, when you look at the text, the issue seems to be the opposite of that. They did think that faith was the power to tell things to change, even to make demons submit, with just a word. And that was that kind of faith they had. But that kind of faith is, as Jesus described it, poor, and small. That’s not the point of faith.
And, as Carson rightly points out, Jesus specifically says, in this passage, “This kind [of spirit] does not go out except by prayer and fasting.” His point seems to be that faith is not necessarily about commanding things or speaking to them at all. Sometimes it’s about the long, unseen work of prayer and fasting.
This puts the whole incident (especially the part about moving mountains) into a larger Biblical framework which, if we’ll give it real thought, will guard us from treating faith like a magic power to remove demons, or mountains. That’s never been the point of faith. The disciples thought it was. But, Jesus says, that’s a poor way to think about faith.