Abdullah bin Ma'qil (may Allah have mercy on him) said: I sat with Ka'b bin Ujrah (may Allah be pleased with him) in the mosque of Kufah and asked him about the saying of Allah Almighty: "Then a ransom of fasting, or charity, or a sacrifice" [Surah al-Baqarah: 196]. He said: I was carried to the Messenger of Allah (peace and blessings be upon him) while lice were falling onto my face. He (peace and blessings be upon him) said: "I did not know that your hardship had reached this extent. Can you find a goat?" I said: "No." He (peace and blessings be upon him) said: "Fast three days, or feed six poor people, half a sa' for each poor person, and shave your head." Ka'b (may Allah be pleased with him) said: This verse was revealed specifically concerning me, and now it is general for all of you.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الحج / 9096