While returning to the University of Erfurt following a visit to his parents in July of 1505, Luther was caught in a sudden and violent summer thunderstorm. Caught on the open road with lightning streaking through the sky, Luther was terrified. The sheeting rain and driving wind obscured his vision and he may well have been reminded of his father's story about demons rustling up an ill-wind to ensnare unsuspecting travellers.

When a shaft of lightning pierced a tree just a few feet ahead of him Luther fell to the road and, wallowing in the churning mud, sent up a desperate plea to St. Anne. He promised that if she interceded on his behalf and his life was spared he would become a monk. It was a hasty and ill thought out plea, chiefly because his father hated the monastic system and everything connected to it and Hans Luther was man who ruled his family with a strong hand.

As it turned out, the storm passed and Luther survived. Two weeks later, in the 17th of July 1505, he presented himself at the gates of the Augustinian Monastery and was admitted as a novice. Hans Luther was incensed. Not only had Luther thrown away years of education, he had also turned his back on his father's plans for him to become a lawyer. Luther's decision to enter the monastery opened up a rift between father and son that lasted for two years.