His physical condition probably contributed to this gloomy frame of mind. Already during his baccalaureate we hear of an illness of his, which awakened in him thoughts of death. A friend, represented by later tradition as an aged priest, said to him on his sick bed, 'Take courage; God will yet make you the means of comfort to many others;' and these words impressed him strongly even then. An accident also, which threatened to be fatal, must have tended to alarm him. As he was travelling home at Easter, and was within an hour's distance of Erfurt, he accidentally injured the main artery of his leg with the rapier which, like other students, he carried at his side. Whilst a friend who was with him had gone for a doctor, and he was left alone, he pressed the wound tightly as he lay on his back, but the leg continued to swell. In the anguish of death he called upon the Virgin to help him. That night his terror was renewed when the wound broke open afresh, and again he invoked the Mother of God. It was during his convalescence after this accident that he resolved upon learning to play the lute.
He was terribly distressed also, a few months after he had taken his degree as Master, by the sudden death of one of his friends, not further known to us, who was either assassinated or snatched away by some other fatality.
Well might the thought even then have occurred to him, while so disturbed in his mind and overpowered by feelings of sadness, whether it would not be better to seek his cure in the monastic holiness recommended by the Church, and to renounce altogether the world and all the success he had hitherto aspired to. The young Master of Arts, as he tells us himself in later years, was indeed a sorrowful man.
Suddenly and offhand he was hurried into a most momentous decision. Towards the end of June 1505, when several Church festivals fall together, he paid a visit to his home at Mansfeld, in quest, very possibly, of rest and comfort to his mind. Returning on July 2, the feast of the Visitation of the Virgin Mary, he was already near Erfurt, when, at the village of Stotternheim a terrific storm broke over his head. A fearful flash of lightning darted from heaven before his eyes. Trembling with fear, he fell to the earth, and exclaimed, 'Help, Anna, beloved Saint! I will be a monk.' A few days after, when quietly settled again at Erfurt, he repented having used these words. But he felt that he had taken a vow, and that, on the strength of that vow, he had obtained a hearing. The time, he knew, was past for doubt or indecision. Nor did he think it necessary to get his father's consent; his own conviction and the teaching of the Church told him that no objection on the part of his father could release him from his vow. Thus he severed himself at once from his former life and companions. On July 16 he called his best friends together to bid them leave. Once more they tried to keep him back; he answered them, 'To-day you see me, and never again.' The next day, that of St. Alexius, they accompanied him with tears to the gates of the Augustinian convent in the town, which he thought was to receive him for ever.