On 31 October 1517 Martin Luther nailed his 95 theses mainly condemning the Catholic Church’s practices on selling indulgences – the act that triggered Reformation. Luther did write explanation of those 95 theses. Below is what he wrote on thesis number 42: Christians are to be taught that the pope does not intend that the buying of indulgences should in any way be compared with works of mercy.
As I have said I understand the pope as a public person, that is, as he speaks to us through the canons. And there are no canons which preach that the value of indulgences is to be compared to works of mercy.
The thesis, moreover, is clear. A command of God has infinitely more value than that which is permitted to exist by man’s word and is in no way commanded by God. The command of God has merit. What man decrees has none.
The objection is made here: “But indulgences are sold for a godly work, for example, for a contribution to a building or for the ransom of captives. Therefore they are meritorious.”
My answer is: I am not speaking about the work, but about the indulgences. Such a work as that could have been done without indulgences, for it is not necessarily bound up with indulgences. Moreover, indulgences which are bestowed without good works confer nothing; they only detract. The work, however, without indulgences does confer something. In the former case we receive benefits for ourselves, in the latter we give them. The former serves the flesh, the latter serves the spirit. Briefly the former satisfies our nature, the latter satisfies the grace of God. Therefore indulgences in themselves are not comparable to a work of mercy.
Likewise a work without indulgences is purer than one with indulgences. Indulgences are somewhat of an imperfection of the work, for the work receives its own reward, indeed much more than its own reward. Therefore people would act in a holier manner if they simply made a contribution for a good work and not for the sake of indulgences. It is not that indulgences in themselves are evil and harmful, but that the perverted abuse of indulgences is harmful, since people would not do such a work of mercy if no indulgences were granted for it. So in this type of work the indulgence becomes the end pursued-indeed a man who looks out for his own interests becomes that end. Man ought rather to do a work of mercy freely and for the sake of God. And he ought to accept only those indulgences which are given to him freely, and not as the result of a financial contribution that he has made. Thus a man should not buy indulgences and the church should not sell them. For both it must be a free gift or it will become a clear case of simony and a foul transaction. But who explains these things to the people when the indulgence sellers say, “Contribute freely, and I will give the indulgence freely?”
At the same time one must fear that by such a perversion of the order of indulgences and works a great idolatry may be perpetrated in the church. If the public is taught to contribute money in order to escape punishment (which I hope does not happen, even though many people probably understand it in this way), then it is evident that they are not contributing for God’s sake, and the fear of punishments, or the punishment itself, is their idol to which they sacrifice. But if such a thing should happen, then such an evil would arise in the church as at one time arose among the pagan Romans when they sacrificed to Febris and other little and harmful deities so that no harm could come to them. So we must be ever watchful for the sake of the people and scarcely entrust such doubtful and dangerous matters to the most learned scholars.
English translation from Luther’s Works, Vol. 31 (underlined emphasis is mine)