Khurappa Jātaka (No.265)
Once the Bodhisatta was a forester, head of five hundred others. They hired themselves out to guide men through the forest. One day, while conducting a caravan, robbers fell on them and all but the Bodhisatta fled; he remained and drove the robbers off. When asked how he could do this, he replied that he who would do heroic deeds must contemn life.
The story was related in reference to a monk who had lost energy in his duties (J.ii.335 f).