"and the owner were warned": We are hereby apprised that he is not liable unless he was warned. "and he did not guard it": to bring (even) a non-paid watcher. Variantly: "and he did not watch it": as befits it—whence they ruled: If he watched it as befits it, he is not liable; if not as befits it, he is liable. If he tied it with a harness and it freed itself and damaged, he is liable for both a tam and a mued, it being written (Ibid. 36) "and its owner did not guard it"—and this is not considered guarding. These are the words of R. Meir.