פירוש על עבודה זרה 91:12

The Talmud now tweaks the analogy. Instead of comparing simply with a mountain and an animal, we can make the comparison with a blemished animal or a dried up tree. Neither are considered to be in their original state and yet both remain permitted even if worshipped. So too the boulder, even though it has been changed by being detached from the mountain, it still remains permitted.