Sahih Bukhari 1816

حَدَّثَنَا أَبُو الْوَلِيدِ ، حَدَّثَنَا شُعْبَةُ ، عَنْ عَبْدِ الرَّحْمَنِ بْنِ الْأَصْبَهَانِيِّ ، عَنْ عَبْدِ اللَّهِ بْنِ مَعْقِلٍ ، قَالَ : جَلَسْتُ إِلَى كَعْبِ بْنِ عُجْرَةَ رَضِيَ اللَّهُ عَنْهُ ، فَسَأَلْتُهُ عَنِ الْفِدْيَةِ ، فَقَالَ : نَزَلَتْ فِيَّ خَاصَّةً ، وَهِيَ لَكُمْ عَامَّةً ، حُمِلْتُ إِلَى رَسُولِ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ وَالْقَمْلُ يَتَنَاثَرُ عَلَى وَجْهِي ، فَقَالَ : مَا كُنْتُ أُرَى الْوَجَعَ بَلَغَ بِكَ مَا أَرَى ، أَوْ مَا كُنْتُ أُرَى الْجَهْدَ بَلَغَ بِكَ مَا أَرَى تَجِدُ شَاةً ؟ فَقُلْتُ : لَا ، فَقَالَ : فَصُمْ ثَلَاثَةَ أَيَّامٍ ، أَوْ أَطْعِمْ سِتَّةَ مَسَاكِينَ ، لِكُلِّ مِسْكِينٍ نِصْفَ صَاعٍ .

Narrated `Abdullah bin Ma'qal: I sat with Ka`b bin 'Ujra and asked him about the Fidya. He replied, This revelation was revealed concerning my case especially, but it is also for you in general. I was carried to Allah's Apostle and the lice were falling in great number on my face. The Prophet said, I have never thought that your ailment (or struggle) has reached to such an extent as I see. Can you afford a sheep? I replied in the negative. He then said, Fast for three days, or feed six poor persons each with half a Sa of food. (1 Sa = 3 Kilograms approx.)