There is a braita: There was once in a certain place an arud which used to injure people. They came and informed Rabbi Hanina ben Dosa. He said to them, “Show me its hole!” They showed him its hole, and he placed his heel over the hole. The arud came out and bit him, and died. He put it on his shoulders and brought it to the Bet Midrash and said to them, “Look, my sons, it is not the arud that kills, it is sin that kills.” At that moment they said, “Oy to the person whom an arud strikes, but oy to the arud that strikes Rabbi Hanina ben Dosa.” (B. Brachot 33.)
* Dictionaries define arud as wild ass. Somehow that does not seem to fit in the context of this episode.