Why did Martin Luther deny that people earn salvation through good works?

Martin Luther’s denial that salvation is earned through good works stemmed from his profound personal struggle with the concept of divine justice and his interpretation of the Gospel.12

As a monk, Luther subjected himself to rigorous asceticism, yet he remained tormented by a sense of his own fundamental sinfulness and an inability to meet the demands of God’s "inexorable justice". He concluded that human beings are inherently too weak to achieve salvation through their own efforts or merits.321

Through his study of St. Paul’s Letter to the Romans, Luther experienced an illumination—often described as a conversion—where he realized that righteousness is not a reward for human effort. Instead, he argued that salvation is a gift of divine grace granted by God alone to those who possess faith. This doctrine of justification by faith alone (sola fide) became the cornerstone of his theology, leading him to reject the Catholic system of indulgences and the idea that human works could contribute to reconciliation with God.1234