הָאוֹמֵר סַמֵּא אֶת עֵינִי, קְטַע אֶת יָדִי, שְׁבֹר אֶת רַגְלִי, חַיָּב. עַל מְנָת לִפְטֹר, חַיָּב.
One who says, "Put out my eye," "Cut off my hand," "Break my leg," he [who did the act] is liable. [One who says, "Put out my eye] on the condition that you will be exempt," he is obligated to pay.
The Gemara explains: As a dilemma was raised before the Sages: What is the halakha with regard to whether a son may let blood for his father? Is he liable for wounding his father? Rav Mattana says that it is written: “And you shall love your neighbor as yourself” (Leviticus 19:18); just as one would want others to heal him when the need arises, one must heal others when the need arises. It is prohibited for one to do to others only those actions that he would not want done to him. Therefore, it is permitted for one to heal his father even if the procedure entails wounding him. Rav Dimi bar Ḥinnana says: This is derived from the juxtaposition between one who strikes a person and one who strikes an animal. Just as one who strikes an animal for medical purposes is exempt from paying restitution, so too, one who strikes a person for medical purposes is exempt from liability.
(a verse implies that it is possible for someone to get lashes for hurting someone without paying for the damage) With regard to one who injures another as well, the verse can be fulfilled in a case where he struck him with a blow that does not cause damage of the value of a prutah