All is grace

This morning's walk was full of color.
The parable in Luke 17:7-10 befuddles me.  Jesus concludes the parable by saying, "When you do all the things commanded you, say, 'We are unprofitable slaves; what we ought to do we have done.'"  Each time it comes up as a Sunday reading, I start looking at all the commentaries and translations I can get my hands on.  The above is a close translation of the Greek.  In the commentaries I find that I have already underlined possible meanings, which I have forgotten since the last time the parable came along.
This week the explanation that I find most appealing is that a slave can earn nothing.  He simply does what his master says with no expectation of a reward or payment.  He does not make a profit by his work.  In that sense he is "unprofitable."  The master may profit from his work, but the slave does not.
Jesus is saying that no amount of service on our part can earn a reward from God because God's goodness to us is unearned.  All is grace.  Our service to God is not bad.  In fact it may be excellent.
But no matter how much we do, we do not profit from our hard work.  God's love is free.