For my own sake, for my own sake, I do it,
for how should my name be profaned?
My glory I will not give to another.
—Isaiah 48:11

Here you see that a self-righteous person is a thief of the divine glory and also an idolater, because he lays claim to God’s glory for himself. He does not pray, “Hallowed be Thy name.” Aspiring to the glory of divinity is a most grievous monstrosity. Here you see the battle between God and the self-righteous concerning glory. The outward glory of this world is nothing compared with it. The self-righteous want to rob God of His glory. And God will not permit this.

The self-righteous man thinks that God will give him rewards for fasting and labor. He thinks that without these God will give him nothing. He thinks precisely that God is someone who will save him through his works, not for the sake of free grace. To this fiction, “God will save me through my works,” he attributes salvation.

This is the most persistent struggle and battle of the world against God. No one wants to rely on God’s glory alone and repudiate all his own merits. For that reason there are so many examples in Scripture which invite us to look to grace alone, whether we eat or whether we drink. So there are endless examples of sins, such as of the robber, that draw us to God’s grace alone.

He wants to make our heart … neither despair because of sins nor be presumptuous because of blessings. … Let the one who has fallen into sin say, “I shall not be condemned because of it.” Let the one who has done well say, “I am not saved thereby.” This teaching applies to the godly only, but for the rest of the crowd it opens the window of carnal liberty. The godly simply cling to God and trust in His grace. They see that the apostles and robbers were saved by the same grace, not by works and merits. This is a thunderbolt against every kind of righteousness.

—Martin Luther
“Lectures on Isaiah: Chapters 40-66” in Works, 17:162–163.