Their word being pledged he came out of the cave, and left his fastness on the rock, and was bound with two ropes. When he saw the mighty men of the Philistines drawing near to seize him, his spirit rose within him, and he brake all his bands, and taking up a jaw bone of an ass that lay near he slew a thousand men, and put to flight the rest by this exploit of valour, whole hosts of armed soldiers giving way to one unarmed man. Thus those who ventured to close with him hand to hand he slew without effort; the others saved themselves by flight. Wherefore to this day the place is called Agon, because there Samson by his great valour achieved a glorious contest.
Source: Letter 19: To Vigilius