“As for the tooth, it is a tooth,” we would have said that it is the tooth with which slaughter is not permissible. But he said, “As for the tooth, it is bone.” Thus, the operative cause is broader than the ruling it produces, for every tooth is bone, but not every bone is a tooth.

The scholars differ over this. Some of them said: “As for the tooth, it is bone,” while also being a tooth. Thus, if it is bone but not a tooth, one component of the composite operative cause—the tooth—is absent, and slaughter with it is lawful.

Other scholars—including Shaykh al-Islam Ibn Taymiyyah, may Allah have mercy on him—said that proper slaughter is not valid with any bone at all, because the Messenger, peace and blessings be upon him, said: “As for the tooth, it is bone.” The reasoning based on its being bone is intelligible: if the bone is from an unslaughtered carcass, it is impure, and an impure object cannot validly serve as an instrument for purification or slaughter. If the bone is from an animal properly slaughtered, slaughtering with it renders it impure. The Prophet, peace and blessings be upon him, forbade cleansing oneself after relieving oneself with bones because doing so contaminates them. Bones are the provision of our brethren among the jinn, for the jinn are granted every bone over which Allah’s Name was mentioned; they find it with the greatest amount of meat upon it. (1) Accordingly, the reason why slaughter with bone is impermissible is intelligible.

Those scholars, however, said that the operative cause is composed of two elements: the tooth and the bone. Had the Prophet, peace and blessings be upon him, intended all bones, he would have said, “Except bone and claw.” Since he did not say this, we know that he intended both meanings.

But the stronger view is that chosen by Shaykh al-Islam, because the reasoning is clear, and the legal principle is that a ruling exists or ceases to exist with the presence or absence of its operative cause.