Two conditions for the cupper, physician, and veterinarian not to be liable for an error:

The first is that their hands must not cause excess harm. Causing excess harm means going beyond what is needed, whether deliberately or by mistake.

The second is that their proficiency be known—that is, that they are skilled in and knowledgeable of their profession. If these two conditions are met, then there is no liability.

Examples:

First: the cupper. Suppose a cupper is known to be proficient, but he makes a mistake and cuts a vein that would not normally be cut in cupping, causing the patient to die. He is liable, because his hand went beyond what was needed, even though it was by mistake. Liability for life and property does not require intent. Thus, a legally insane person is liable if he destroys property, kills an animal, or takes a life, except that his deliberate act is deemed an error.

Second: the physician. Suppose he intends to perform an operation—say, an appendectomy—and carries it out, but the scalpel goes beyond what is needed: he makes a larger incision than necessary, and the patient dies. In this case, he is liable, because his hand caused excess harm.

The same applies in prescribing medicine. A physician prescribes medicine for someone, saying, for example, “Take five tablets of this medicine,” when three would suffice. The patient takes the five tablets and dies. The physician is liable, because his hand has in fact caused excess harm: he erred in his assessment, and is therefore liable, even though he is not sinful.

The second condition, “provided their proficiency is known,” means that he must be experienced in