In Luke 17:6 Jesus tells his disciples that if they had faith the size of a mustard seed they could say to a mountain, “Hop into the sea,” and it would do it. Jesus says this in response to the disciple’s request for faith. They had thought that they couldn’t obey Christ when he told them to forgive their brother when he committed the same sin seven times and asked to be forgiven. When you think about this, it is a pretty tall order.
But how is Jesus’ response an answer to their request. They aren’t asking how much faith they will need to forgive their repentant brother, they are asking for more faith itself. They believe that faith does something and they need more of it in order to be more obedient. My guess is that they thought of faith like a muscle. If it is bigger or you have more of it, you can lift more weight. If Jesus gives a difficult command, more faith will be necessary in order to obey.
Jesus’ answer, however, doesn’t really help, other than to be a little bit confusing. He says if they have a little tiny bit of faith, they could cast a mountain into the sea. Does this mean that no one has ever had that much faith? In other places Jesus seems to indicate that a mustard seed is one of the smallest seeds around (cf. Mk. 4:31). There have been no mountains, either before or after, that have jumped into the sea. They never even jumped at the voice of Christ. Does that mean that Jesus didn’t have that much faith either?
Here’s how I think it works: It is true that what Jesus told his disciples was hard to obey. Forgiving a brother who sins against you once is hard enough, but to forgive him seven times for the same sin in the same day is virtually impossible (seven was not a literal number, which only makes it worse). The normal man needs something more than we have to be obedient to this command. I believe Jesus’ response is to say that more faith is not what we need. What we need is to be faithful to our Lord and to be obedient to his commands.
In the text after verse six, Jesus says that if we had a slave who had worked in the field all day we wouldn’t ask him to sit down so we could wait on him after a long hard day. Instead we would tell him to get cleaned up and feed us. After all, the relationship is one of service, not friendship. A slave is a belonging, a tool, a thing to be used for comfort. The owner does not treat his slave as if he were a buddy.
What’s more, the slave’s attitude is that he is only doing what was commanded, it is his duty. The slave knows his place and wouldn’t even imagine that he might be compensated or served when the day in the field is finished. In the same way, Jesus says we should have this same attitude toward God when he gives us a hard command. We are only servants who are doing what we are commanded to do.
What does faith have to do with all this? Believing that God is God and we are only unworthy servants is what faith is. Faith does nothing of itself. If we believe in God, if we trust in God we will do the things he has commanded. And God has promised that as we do what we have been commanded to do because Jesus is Lord, he will give us the power to succeed and will be in us doing the work. In another place in the Bible the Apostle commands us to work out our salvation with fear and trembling, for it is God who works in us for his good pleasure (Phil. 2:12-13).
So faith doesn’t actually do anything. God commands and we obey. We obey because we believe that he is God and we are his unworthy servants. Because we believe God, or because we have faith in God, or because we trust God, we are being obedient. As we go on in life, trusting God’s promises, he lives in us and empowers us to do what he has commanded us to do. This is what living by faith means.
This is also what Jesus meant when he said that we didn’t need more faith to forgive our brother. What we need is a faithful God and a desire to serve him as unworthy servants. And we show that this is true by forgiving our brother seven times in the same day for the same sin.