Abu Hurairah:
The Messenger of Allah (ﷺ) as saying: No retaliation is payable for a wound caused by a dumb animal, for a mine, and for a well. On the treasure found buried in the land there is a fifth.
Abu Dawud said: A dumb animal means an animal which is free and has not tether, and there is no one (as a watchman) with it. It causes harm by day and not by night.