Narrated 'Abdullah bin Maqal:
I sat with Ka'b bin Ujra in this mosque, i.e. Kufa Mosque, and asked him about the meaning of:--"Pay a ransom (i.e. Fidya) of either fasting or - - - - (2.196) He said, "I was taken to the Prophet while lice were falling on my face. The Prophet ﷺ said, 'I did not think that your trouble reached to such an extent. Can you afford to slaughter a sheep (as a ransom for shaving your head)?' I said, 'No.' He said, 'Then fast for three days, or feed six poor persons by giving half a Sa of food for each and shave your head.' So the above Verse was revealed especially for me and generally for all of you."
Sahih al-Bukhari, Vol. 6, Book of Prophetic Commentary on the Qur'an, Hadith 42
Sahih al-Bukhari, Book of Prophetic Commentary on the Qur'an, Hadith 42