Ash Shaykh Al Bassaam mentions in Tawdeehul Ahkaam 7/466:
It is mentioned in the Explanation of Al Iqnaa’:
The one hitting should avoid [hitting] the head, face, private part, stomach – from the males and females – and the places [that] if one hits will kill [the person being hit], since it is obligatory to avoid it, because hitting it [i.e. that place] will lead to killing, and it is that which he isn’t commanded with.
Majid Jawed Al Afghanee