"Who among you would say to your slave who has just come in from plowing or tending sheep in the field, 'Come here at once and take your place at the table'? Would you not rather say to him, 'Prepare supper for me, put on your apron and serve me while I eat and drink; later you may eat and drink'? Do you thank the slave for doing what was commanded? So you also, when you have done all that you were ordered to do, say, 'We are worthless slaves; we have done only what we ought to have done!'"
How do we reconcile these harsh words of Christ: "say, 'we are worthless slaves'" and "does the master thank a slave for doing what is commanded?" with what Christ says elsewhere: "those who are considered worthy of a place in heaven..." (Luke 20.35)? If we are worthless slaves how can we be worthy to enter the everlasting realms of paradise?
There are two points that need addressed: "worthless slaves" and "does a master thank a slave?" On the point of being worthless slaves, note Our Lord says "say to yourselves." He is establishing the reality of who we are in respect to him and teaching us how to view ourselves. He does not say "I will call you worthless slaves" but rather "call yourselves worthless slaves." This disposition of servitude is utterly necessary for the servant of God. The human heart is all too ready to preen itself, look in the mirror, imagine the good it has done and contemplate being thanked by God for it. If that is our view we have a great height from which to fall. "He has scattered the proud in their conceit." (Luke 1.51)
If we praise ourselves for the good we have done we usurp the part of God. We act in his place, like servants taking over the part of the master, like laborers paying themselves. In doing so we subtlety start thinking ourselves the creator of the good we have done, the origin of the ideas for what to do. The solution is humility. If we meditate on Christ's words it is clear what our part is: to work as laborers and not view ourselves as worthy of thanks. Humility is truth and truth is liberation. Consider the angels. They constantly inspire us to perform good works which we are sometimes able to do, and then we get - and take - credit for the idea! Do you imagine the angels feel slighted for not receiving the credit? We should do good in secret and then try to give the credit to others to build up their spirit.
The second point is the issue of being thanked. The master does not thank the servant. In fact nowhere in Christ's words or the entire New Testament can I find where it says God will thank us. It does say everywhere that we thank God, and God willing, will thank him throughout eternity.
What God will do for us in the end if we are found worthy by obeying him, is written in the end of the Word, throughout the book of Revelation. "To everyone who conquers, I will give permission to eat from the tree of life that is in the paradise of God...I will give some of the hidden manna and a white stone with a new name that no one knows except the receiver...I will give authority over the nations...I will give the morning star...I will clothe you in white robes and confess your name before my Father and the angels...I will make you a pillar in the temple of my God; you will never go out of it. I will write on you the name of my God and my own new name...I will come in to you and eat with you, and you with me...I will guide you to springs of the water of life and wipe away every tear from your eyes." (Revelation 1-7)