They may have needed to have their confidence bolstered. They asked to have their faith increased. Jesus replied, "If you had faith the size of a mustard seed, you could get a mulberry tree to jump in the ocean just by telling it to."
When I was in the 5th grade, somebody gave me a necklace with a mustard seed encased in a plastic ball. I used to look at that tiny seed and wonder why the trees around me weren't listening to me. And I lived in a place where the trees weren't very big.
Other Bible readers, like me, have been troubled by this passage. Is Jesus promising us that we will be able to perform superhuman actions or great magic tricks? Or, is Luke using hyperbole or even metaphoric talk?
So, today, I turned, as I often do, to Fred Craddock in Preaching through the Christian Year C. He points out that the "if" in Jesus' statement can be translated in two ways, The word "if" could be describing a condition contrary to fact. Or, "if" could be describing a condition according to fact.
Try substituting "since" for "if" to see how this would sound in English. Craddock says Jesus is giving them "an indirect affirmation of the faith they have and an invitation to live and act out in that faith. They ask for an increase in their faith. He says that the faith you already have is effective and powerful beyond your present realization."
Do we deserve any special praise for following Christ? for accomplishing what he has required of us? Or, as Christ's servants, aren't we when we think of ourselves as doing good as dramatic as getting a tree to jump in the lake, aren't we even then just doing our job, just doing what Christ's servants are to do?