Who bears the penalty (Fidya) if a non-Muhrim (Halal) shaves the head of a Muhrim with his permission?

Primary text

The Fidya is incumbent upon the one whose head was shaved, regardless of whether the shaver was in the state of Ihram (Muhrim) or not (Halal), provided it was done with the permission of the one being shaved. This is because the act involved removing something prohibited for the person in Ihram, thus necessitating the penalty upon him, similar to when a Muhrim shaves his own head.