He replied:

If the person who was beaten is under his father’s guardianship, neither his settlement nor his release of the other party from liability is valid. Whatever his father paid because of this false accusation, he may recover from whoever wrongfully made him pay it, whether or not the son released that person from liability. The person who was beaten is entitled to inflict an equivalent beating on any of his accusers who called for him to be beaten, provided that he had not previously been known for wrongdoing.

Al-Nu‘mān ibn Bashīr stated that this was the ruling of Allah and His Messenger, as reported by {Abū Dāwūd and others. When some people asked him to beat a man on suspicion, he said: “If you wish, I will beat him for you; but if your property is not found in his possession, I will beat you just as I beat him.” They asked: “Is this your ruling?” He replied: “This is the ruling of Allah and His Messenger.”}

This concerns beating someone who was not known for wrongdoing. Beating someone known for wrongdoing is a different matter. Retaliation in kind for beating, slapping, and similar acts is established in reports from the Rightly Guided Caliphs and other Companions and Successors. It is also established in the Sunnah of the Messenger of Allah, may Allah bless him and grant him peace, and was expressly affirmed by several leading scholars, including Ahmad ibn Hanbal. Although many jurists do not recognize retaliation in kind in such cases, holding instead that discretionary punishment applies, the former view is correct.

But may the father exact the retaliation to which his son is entitled, or must he leave it until the son reaches adulthood? There is a well-known disagreement among scholars concerning this. If the son is already an adult, however, he himself has the right to exact corporal punishment and to retain that right.