Mishkat al-Masabih 443

Abū Hurayra reported that the Messenger of Allah said: ‘Under every hair there is sexual impurity, so wash the hair and cleanse the skin thoroughly.’

Abū Dāwūd, al-Tirmidhī, and Ibn Mājah transmitted it. Al-Tirmidhī called it gharīb and said that its transmitter, al-Ḥārith ibn Wajīh, was a shaykh whose reliability was not strong.