Narrated Ka`b bin 'Ujra: I came to the Prophet (ﷺ) and he said to me, "Come near." So I went near to him and he said, "Are your lice troubling you?" I replied, "Yes." He said, "(Shave your head and) make expiation in the form of fasting, Sadaqa (giving in charity), or offering a sacrifice." (The sub-narrator) Aiyub said, "Fasting should be for three days, and the Nusuk (sacrifice) is to be a sheep, and the Sadaqa is to be given to six poor persons."
Source: sunnah.com
Other translations
Arabic
حَدَّثَنَا أَحْمَدُ بْنُ يُونُسَ، حَدَّثَنَا أَبُو شِهَابٍ، عَنِ ابْنِ عَوْنٍ، عَنْ مُجَاهِدٍ، عَنْ عَبْدِ الرَّحْمَنِ بْنِ أَبِي لَيْلَى، عَنْ كَعْبِ بْنِ عُجْرَةَ، قَالَ أَتَيْتُهُ يَعْنِي النَّبِيَّ صلى الله عليه وسلم فَقَالَ " ادْنُ ". فَدَنَوْتُ فَقَالَ " أَيُؤْذِيكَ هَوَامُّكَ ". قُلْتُ نَعَمْ. قَالَ " فِدْيَةٌ مِنْ صِيَامٍ أَوْ صَدَقَةٍ أَوْ نُسُكٍ ". وَأَخْبَرَنِي ابْنُ عَوْنٍ عَنْ أَيُّوبَ قَالَ صِيَامُ ثَلاَثَةِ أَيَّامٍ، وَالنُّسُكُ شَاةٌ، وَالْمَسَاكِينُ سِتَّةٌ.
sunnah.com