From Heiko Oberman's book:
"Yet, as Luther pointed out at the beginning of his professional career and at the end of his life, all his discoveries could not exhaust the wealth of the Scriptures. In his early Psalm lectures he said: "If you, O human being, cannot grasp some scriptural passage completely and are capable of unveiling the concealed truth only in part--be it as large as it may--then know that there is witness there that points past you and will only be revealed to you or others in the future." One might assume that this was a beginner exercising the humble restraint befitting a monk and that the expert, the Reformation Luther, would overcome it. But that was not the case. A note in Latin was found next to Luther's deathbed; he wrote it two days before he died:
No one can understand Virgil in his Bucolics and Georgics unless he has spent five years as a shepherd or farmer. No one understands Cicero in his letters unless he has served under an outstanding government for twenty years. No one should believe that he has tasted the Holy Scriptures sufficiently unless he has spent one hundred years leading churches with the prophets. That is why: 1. John the Baptist, 2. Christ, 3. the apostles were a prodigious miracle. Do not profane this divine Aeneid, but bow to it and honor its vestiges.
In view of Luther's life-long struggle to clarify the Scriptures in questions crucial to salvation, his "last words" may sound like a confession of resignation. This, however, is misleading. The point is rather that to study the Scriptures is like a journey--full of surprising discoveries.
This is followed by the statement "We are beggars" in German, and in Latin again, "That is true."
A doctor of theology for thirty-four years, practiced in the translation and exegesis of Scripture--notwithstanding all this experience, he had to admit that he was overwhelmed by the depth and wealth of the Scriptures, which no man would ever fathom in a single lifetime.
In view of Luther's life-long struggle to clarify the Scriptures in questions crucial to salvation, his "last words" may sound like a confession of resignation. This, however, is misleading. the point is rather that to study the Scriptures is like a journey--full of surprising discoveries. He once compared his scriptural studies to a walk through a forest: "There is hardly a tree in this forest that I have not shaken and obtained apples or picked berries from." Certainly his statement did not lack pride, but neither did it make any claim to his having finished with the Scriptures.
During his last, ten-year(!) course of lectures on the Book of Genesis (1535-45), Luther took another extended walk through the woods and gathered the fruits of his roamings into concentrated summaries of his theology. Although these lectures deserve to be used as an introduction to Luther's world of faith, they have nearly fallen into oblivion owing to the prevailing interest in the young Luther as well as to the complex history of how they have come down to us.
The theme throughout is the wild rage of the Devil, who seeks unceasingly to destroy the Son of God everywhere: "He is his target," because His birth and death are the agents of divine redemption. The Devil's battle against Christ makes the "walk through the woods" necessary and divests it of its arbitrariness. Luther's single-mindedness is demonstrated in his interpretation of the story of Jacob's ladder. Jacob was fleeing from his brother Esau. One night he dreamt of a ladder that reached into Heaven, with angels of God ascending and descending it (Gen. 28.12-14). Luther was able to illustrate the whole of his Reformation theology by means of Jacob's dream at Bethel: through God's Word and spirit, Christians are led up to Heaven and, in their faith, united with Christ. Christ Himself, however, descends to lead Christendom. The ladder connecting Heaven and earth is the incarnation of God; it is what the Devil hates most and is perpetually fighting against. The Devil wants to tear the faithful away from Christ, their ladder to Heaven.
Luther had long been a master in finding ever new and graphic ways of combining the various realms of god's work--in Christ, in justification, in the Creation--into a single vision. Now the kingdom of the Devil had received sharp contours as well. thirty years earlier "sing, world, and Devil" had still formed the traditional medieval phalanx of evil. To escape the Devil one had had to avoid the world and seek salvation where there was no room for sin--most safely at a monastery. But now the Devil was the opponent of the world created by God, seeking to destroy all the forces involved in protecting God's creation: family and economy, state and Church. Luther's walk had taken him out of the monastery and into the world."
(Luther. Man between God and the Devil. Oberman. pp. 166-168)
--I have to say, this quote above helps me understand Luther's lasts words better. The Bible was for him inexhaustible supply and food for thought. He did not expect that he could ever fully plum its depths. Everywhere he found it speaking about his dear Lord Jesus Christ. We can refresh ourselves from his attitude easily. He also offers us nourishment, and I am grateful for it.
The commentary on Genesis is available free at I-books. I have lately peeked into it and was greatly intrigued by it. Thought the commentaries are 500 years old they are thorough and deep and show forth Luther's great experience in life and in scripture. They are very worthwhile reading, as Oberman says, though apparently neglected.