Ka'b bin 'Ujrah (RAA) narrated, ‘I was carried to the Prophet (ﷺ) and the lice were falling over my face. He said, “I did not know that your disease is hurting you as much as what I see. Can you sacrifice a sheep?” I said, ‘No.’ He then said. “Fast for three days or feed six poor people, half a Sa’ each.” Agreed upon.

وَعَنْ كَعْبِ بْنِ عُجْرَةَ ‏- رضى الله عنه ‏- قَالَ: { حُمِلْتُ إِلَى رَسُولِ اَللَّهِ ‏- صلى الله عليه وسلم ‏-وَالْقَمْلُ يَتَنَاثَرُ عَلَى وَجْهِي, فَقَالَ: " مَا كُنْتُ أَرَى اَلْوَجَعَ بَلَغَ بِكَ مَا أَرَى, تَجِدُ شَاةً ? قُلْتُ: لَا.‏ قَالَ: " فَصُمْ ثَلَاثَةَ أَيَّامٍ, أَوْ أَطْعِمْ سِتَّةَ مَسَاكِينَ, لِكُلِّ مِسْكِينٍ نِصْفُ صَاعٍ " } مُتَّفَقٌ عَلَيْهِ [1]‏ .‏