Luther enrolled at the University of Erfurt in 1501. In 1505 he began to study law, at his father's wish. On July 2, 1505, he was caught in a violent thunderstorm on the road near the village of Stotternheim. Thrown to the ground by a bolt of lightning that struck close by, he cried out in terror to St. Anne, the patron saint of miners: “Help, St. Anne! I will become a monk.” Two weeks later, to his father's fury, he kept the vow and entered Erfurt's Augustinian monastery.
The years that followed were not peaceful ones. Luther threw himself into monastic life: fasting, confession, long hours of prayer. He wanted to be certain where he stood with God, and the certainty never came. He confessed constantly, sometimes for hours, terrified of sin he couldn't even name. It was here, under the guidance of his mentor Johann von Staupitz, that the questions began to form that would eventually take him to Wittenberg.