Here we should steadfastly maintain our teaching so that we never let any work take credit for gaining the favor and grace of God, for liberating us from sin, and for bringing us to heaven. My merit is worthless for this. And if someone should want to use it for this, I must trample it underfoot and damn it to the devil himself in hell, as a thing that denies Christ and seeks to hinder my faith. All that avails here is the fact that God has given all this free, out of pure grace, by sending Christ, His Son, and letting Him die for me, announcing and granting this to me, and commanding me simply to believe it and to be baptized in it. None of my works has anything to do with this, but it is purely a gift, bestowed from heaven and brought to me by Christ. Let all merit be simply discarded here in favor of the conclusion that it is impossible to obtain grace and the forgiveness of sins in any other way, manner, or measure than by hearing the Word of God about Christ and by receiving it through faith. And why should we brag about our merit in order to make God applaud us? They themselves and all the saints have to pray in the Lord’s Prayer every day as long as we live: “Forgive us our debts.” And yet these desperate saints have the audacity to say that a man in mortal sin can prepare himself for grace, and then can merit eternal life!
How do you deal with the fact that there are so many passages about reward and merit? For the benefit of the simple people, we give the answer now that these are simply intended to comfort Christians. Once you have become a Christian and have a gracious God and the forgiveness of sins, both of past sins and of those that cling to you every day, a certain result will be that you will have to do much and suffer much on account of your faith and your Baptism. As these three chapters have shown in detail, the devil himself, together with the world and the flesh, will attach himself to you and torment you from every side, making the world seem too narrow for you. If we were left to be stuck in this, without Word or consolation, we would despair and say: “Who wants to be a Christian or preach or do good works? You see what happens to them. The world tramples them underfoot, defames and slanders them, and tries every kind of villainy and evil trick on them, finally robbing them of their honor, their property, and their life. All Christ can call me is poor, troubled, hungry, meek, peaceable, afflicted, and persecuted! Is this supposed to last forever and never change?”
Then He has to speak out, strengthening and comforting us and saying: “Now you are in grace, and you are the children of God. Though you have to suffer for that in the world now, do not let it frighten you. Hold on tight, and do not let what you see tire you out or wear you down. Let everyone do his duty. If this causes him trouble, it will not do him any damage. He should know that the kingdom of heaven is his and that he will be richly repaid.” Repaid, but how? We already have it through Christ, apart from, and prior to, any action of ours. As St. Paul says (1 Corinthians 15:41), God will make you a big, bright star and give you a special gift, even in this life. Even here on earth, a Christian can obtain so much from God through his prayer and good works: He can save a whole country, prevent war, famine, and pestilence. This is not because the work is so precious in its own right, but because He has promised this to strengthen and comfort us and to keep us from thinking that our works, troubles, and sorrows have been lost and forgotten.
Luther’s Works Volume 21:289-291