Sayyiduna Ka'b bin Ujrah (may Allah be pleased with him) said: This verse was revealed concerning me. So I came to the Prophet (peace and blessings be upon him), and he (peace and blessings be upon him) said: "Come closer." So I came closer two or three times, and he (peace and blessings be upon him) said: "Are your lice troubling you?" (Ibn Awn said: I think he said: Yes.) So he (peace and blessings be upon him) ordered me to fast, or give charity, or offer a sacrifice, whatever was easy.
Ibn Awn said: I forgot what he said about the fasting and the charity, so I mentioned it to Ayyub al-Sakhtiyani, and he said: I too heard this hadith from him. I asked: How does it go? He said: Fasting three days, or charity to six poor people, or a sacrifice, whatever is easy. And Ayyub used to say that he (peace and blessings be upon him) said: "Are the lice of your head troubling you?"
Hadith Referenceالمعجم الكبير للطبراني / باب الكاف / 16281