What is the specific amount of expiation due for each falling hair?

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For each falling hair, the expiation is one Mudd of food. This is the opinion held by Al-Hasan, Ibn Uyaynah, and Al-Shafi'i concerning anything less than four hairs. The evidence for this ruling stems from the general principle that what is guaranteed in totality is guaranteed in its parts, similar to hunting game. Furthermore, the ruling reverts to food (It'am) because the Lawgiver substituted food for an animal in the expiation for hunting, and here the option between animal sacrifice and food is given, thus food should be mandated where blood sacrifice is not mandatory.