What is the meaning of the parable in Luke 17:7-10? In the first verse of Luke 17:5-10, the disciples ask Jesus to increase their faith. Here is the full passage, in the New King James Version (NKJV):

5 And the apostles said to the Lord, &quot;Increase our faith.&quot;
6 So the Lord said, &quot;If you have faith as a mustard seed, you can say to this mulberry tree, 'Be pulled up by the roots and be planted in the sea,' and it would obey you. 7 And which of you, having a servant plowing or tending sheep, will say to him when he has come in from the field, 'Come at once and sit down to eat'? 8 But will he not rather say to him, 'Prepare something for my supper, and gird yourself and serve me till I have eaten and drunk, and afterward you will eat and drink'? 9 Does he thank that servant because he did the things that were commanded him? I think not. 10 So likewise you, when you have done all those things which you are commanded, say, 'We are unprofitable servants. We have done what was our duty to do.'&quot;

The beginning of Jesus' reply in 17:6 seems to be directly connected. But I am having trouble figuring out what 17:7-10 have to do with what was being said. This heavily implies I am not interpreting it correctly, as the Bible tends to make sense in context.
My interpretation of the parable is that God does not owe us anything because of what we do for Him. I just can't figure out what that has to do with the disciple's request for greater faith. There must be some commonly understood explanation for why Jesus used this parable as part of his reply to the disciples' request, but I have been unable to find any easily web-available commentary that addresses the subject.
Increase our Faith! = Make it Easier! (or Lighten the Burden!)

Just before the parable, Jesus says (paraphrasing, for brevity)


Don't be a stumbling block...or else!
Rebuke and forgive your brothers.
Forgive a brother even if he continually sins against you.


The disciples' response is, "Increase our faith!" (πιστις 4102, "trust" "belief" "conviction")

It sounds like the disciples want some help doing what Jesus is telling them to do, because he is not asking them to do something easy. They ask for faith, perhaps because believing better/trusting more would make it easier to endure the difficulties of the life to which Jesus is calling them.

In regards to doing good things, the disciples were at least occasionally at odds with each other about who was better.
The parable about the servant is a way of saying that if you do all these good things, you are still only doing what Jesus has told you to do.

It's almost as if being a heroic Christian is the bare minimum. Increase my faith!