When two gospel writers place the same story in different contexts, that instantly gets my attention. Such is the case with the parable of the mustard seed. What is each writer trying to say, in their own unique ways? In Matthew 17:20, the mustard seed is referred to after the disciples discover that they cannot cast out demons: they have insufficient faith. Here, in Luke, the mustard seed is alluded to in response to the plea of the disciples that Jesus “increase/add to our faith” (Luke 17:3). But note that the first few verses of Chapter 17 (1-4) are all about forgiveness (“… you must forgive”). And so, it seems that Luke connects the ability to forgive directly to one’s faith. More than that, by immediately following these teachings with a sermon on the topic of the servanthood of a slave, Luke seems to connect forgiveness with faith, and a forgiving faith with discipleship.
The flow of thought seems to go something like this… If, in your discipleship, you sin, or another sins against you, a rebuke is in order. And, if the result is repentance, then forgiveness must be shown (Luke 17:1-4). If you had faith even as wee as a mustard seed, you would have mighty faith indeed. Actually, you would even have faith sufficient to forgive each other (Luke 17:5-6). Yet, this is nothing to boast about. After all, should a big fuss be made over a slave who does the minimum that is expected of him/her? (This is Luke’s favorite household metaphor – that of master-slave. He uses it over and over again – see 12:35-40, 42-48; 13:25-27; 14:16-24; 16:1-13.) And so, your faith as a disciple, and the forgiveness you show as a disciple, are simply component parts of your discipleship. The only thing that you have a right to say concerning all of this, is this: “… we have done only what we ought to have done” (Luke 17:10).
