Hadith 1:152
Narrated Abu Hurairah (RAA):
Allah's Messenger (Peace be upon him) said: "There is Janabah (trace of sexual impurity) under every hair, so wash your hair and cleanse the skin." Abu Dawud and at-Tirmidhi transmitted it but they declared it to be weak.
وَعَنْ أَبِي هُرَيْرَةَ - رضى الله عنه - قَالَ: قَالَ رَسُولُ اَللَّهِ - صلى الله عليه وسلم -{ إِنَّ تَحْتَ كُلِّ شَعْرَةٍ جَنَابَةً, فَاغْسِلُوا اَلشَّعْرَ, وَأَنْقُوا اَلْبَشَرَ } رَوَاهُ أَبُو دَاوُدَ, وَاَلتِّرْمِذِيُّ وَضَعَّفَاه ُ (151)
Original Reference: Bulugh al-Maram 124