Q: Two people got into a fight. One of them hit the other, who retaliated forcefully and injured the first person. Is the second person liable for the injury?

A: A person is allowed to hit back to protect himself from an attacker. However, if he could protect himself by inflicting minimal injury and he injured the attacker seriously, he is liable for the excessive damage (C.M. 421:13).

Similarly, once the parties have separated and the victim is no longer threatened, he may not hit the attacker back. If he subsequently hits and injures the attacker after cooling down, he is liable. There is a dispute whether he is liable if he hit back immediately after separating, while still heated by the fight, unless there is concern that the attacker might continue to hit him (see Sma 421:24; Taz 421:13; Pischei Choshen, Nezikin, 2:[30].)

If two people willingly agree to a wrestling match and one injures the other while throwing him down, he is exempt. The reason is that the two willingly submit themselves to potential injury and forgo claims, and it is difficult to control exactly how one fells his opponent (421:5; see P.C., Nezikin 2:10[34]).