For Luther, the importance of study was so interwoven with his discovery of the true gospel that he could never treat study as anything other than utterly crucial and life-giving and history-shaping. Study had been his gateway to the gospel and to the Reformation and to God. We take so much for granted today about the truth and about the word that we can hardly imagine what it cost Luther to break through to the truth, and to sustain access to the word. Study mattered. His life and the life of the church hung on it. And so, Luther studied, and preached, and wrote more than most of us can imagine.

Luther was not the pastor of the town church in Wittenberg, but he did share the preaching with his pastor friend, Johannes Bugenhagen. The record bears witness to how utterly devoted he was to the preaching of Scripture. For example, in 1522 he preached 117 sermons, the next year 137 sermons. In 1528, he preached almost 200 times, and from 1529 we have 121 sermons. So the average in those four years was one sermon every two and a half days. And all of it arose from rigorous, disciplined study.

That is what study was to Luther — taking a text the way Jacob took the angel of the Lord, and saying, “It must yield. I will hear and know the word of God in this text for my soul and for the church!”

Source: He Dared to Defy the Pope by John Piper