Sahih Muslim Book - 15, Hadith - 2884

وَحَدَّثَنَا أَبُو بَكْرِ بْنُ أَبِى شَيْبَةَ حَدَّثَنَا عَبْدُ اللَّهِ بْنُ نُمَيْرٍ عَنْ زَكَرِيَّاءَ بْنِ أَبِى زَائِدَةَ حَدَّثَنَا عَبْدُ الرَّحْمَنِ بْنُ الأَصْبَهَانِىِّ حَدَّثَنِى عَبْدُ اللَّهِ بْنُ مَعْقِلٍ حَدَّثَنِى كَعْبُ بْنُ عُجْرَةَ - رضى الله عنه - أَنَّهُ خَرَجَ مَعَ النَّبِىِّ -صلى الله عليه وسلم- مُحْرِمًا فَقَمِلَ رَأْسُهُ وَلِحْيَتُهُ فَبَلَغَ ذَلِكَ النَّبِىَّ -صلى الله عليه وسلم- فَأَرْسَلَ إِلَيْهِ فَدَعَا الْحَلاَّقَ فَحَلَقَ رَأْسَهُ ثُمَّ قَالَ لَهُ « هَلْ عِنْدَكَ نُسُكٌ ». قَالَ مَا أَقْدِرُ عَلَيْهِ. فَأَمَرَهُ أَنْ يَصُومَ ثَلاَثَةَ أَيَّامٍ أَوْ يُطْعِمَ سِتَّةَ مَسَاكِينَ لِكُلِّ مِسْكِينَيْنِ صَاعٌ فَأَنْزَلَ اللَّهُ عَزَّ وَجَلَّ فِيهِ خَاصَّةً (فَمَنْ كَانَ مِنْكُمْ مَرِيضًا أَوْ بِهِ أَذًى مِنْ رَأْسِهِ) ثُمَّ كَانَتْ لِلْمُسْلِمِينَ عَامَّةً.

Kab bin Ujrah [may Allah be pleased with them] narrated that he went out with the Messenger of Allah (SAW) in Ihram, and his heas and beard was infested with lice. News of that reached the Prophet (SAW) and he sent for him and called the barber to shave his head, then he said to him: “Do you have an animal to sacrifice?” He said: “I cannot afford that.” So he told him to fast for three days, or feed to to six persons , giving a Sa to each two poor persons. Then Allah revealed the verse “And whosoever of you is ill or has an ailment in his scalp (necessitating shaving)” specifically about him, then it applies to all the Muslims in general.