Judges 3:31

An ox goad — As Samson did a thousand with the jaw — bone of an ass; both being miraculous actions, and not at all incredible to him that believes a God, who could easily give strength to effect this. It is probable Shamgar was following the plough, when the Philistines made an inroad into the country. And having neither sword nor spear, when God put it into his heart to oppose them, he took the instrument that was next at hand. It is no matter how weak the weapon is, if God direct and strengthen the arm.