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Martin Luther on idolatry
So that it may be understood and remembered, I must explain this a little more plainly by citing some everyday examples of the opposite. There are some who think that they have God and everything they need when they have money and property; they trust in them and boast in them so stubbornly and securely that they care for no one else. [6] They, too, have a god—mammon by name, that is, money and property—on which they set their whole heart. This is the most common idol on earth. [7] Those who have money and property feel secure, happy, and fearless, as if they were sitting in the midst of paradise. [8] On the other hand, those who have nothing doubt and despair as if they knew of no god at all. [9] We will find very few who are cheerful, who do not fret and complain, if they do not have mammon. This desire for wealth clings and sticks to our nature all the way to the grave.
So, too, those who boast of great learning, wisdom, power, prestige, family, and honor and who trust in them have a god also, but not the one, true God. Notice again, how presumptuous, secure, and proud people are when they have such possessions, and how despondent they are when they lack them or when they are taken away. Therefore, I repeat, the correct interpretation of this commandment is that to have a god is to have something in which the heart trusts completely.
There is, moreover, another false worship. This is the greatest idolatry that we have practiced up until now, and it is still rampant in the world. All the religious orders are founded upon it. It involves only that conscience that seeks help, comfort, and salvation in its own works and presumes to wrest heaven from God. It keeps track of how often it has made endowments, fasted, celebrated Mass, etc. It relies on such things and boasts of them, unwilling to receive anything as a gift of God, but desiring to earn everything by itself or to merit everything by works of supererogation, just as if God were in our service or debt and we were his liege lords.39 [23] What is this but to have made God into an idol—indeed, an “apple-god”—and to have set ourselves up as God? But this reasoning is a little too subtle and is not suitable for young pupils.
14 “Now therefore fear the LORD and serve him in sincerity and in faithfulness. Put away the gods that your fathers served beyond the River and in Egypt, and serve the LORD. 15 And if it is evil in your eyes to serve the LORD, choose this day whom you will serve, whether the gods your fathers served in the region beyond the River, or the gods of the Amorites in whose land you dwell. But as for me and my house, we will serve the LORD.”