William Barclay from Jesus As They Saw Him:
He [the shepherd] had his rod and his staff. The staff was a long crooked stick. Always the shepherd walked with it in his hand, and, when a sheep showed signs of straying, he would stretch out and pull it back with the crook. He carried the rod at his belt. It was a stout piece of wood, perhaps three feet long, with a lump of wood the size of an orange at one end of it. With this the shepherd fought the battles of the flock, using it to drive off wild beasts and to defend the flock against the robbers who would steal the sheep.
