Ash-Shama'il Al-Muhammadiyah, Book 4, Hadith 32 (English) ⓘ

Hazrat Anas (Radiallahu anhu) reports, "Sayyidina Rasulullah (Sallallahu alaihe wasallam) often rubbed oil in his head and also often combed his beard. He put a cloth over his head, which became like an oil cloth due to the frequent use of oil."

حَدَّثَنَا يُوسُفُ بْنُ عِيسَى، قَالَ‏:‏ حَدَّثَنَا وَكِيعٌ، قَالَ‏:‏ حَدَّثَنَا الرَّبِيعُ بْنُ صَبِيحٍ، عَنْ يَزِيدَ بْنِ أَبَانَ هُوَ الرَّقَاشِيُّ، عَنْ أَنَسِ بْنِ مَالِكٍ، قَالَ‏:‏ كَانَ رَسُولُ اللهِ صلى الله عليه وسلم يُكْثِرُ دَهْنَ رَأْسِهِ وَتَسْرِيحَ لِحْيَتِهِ، وَيُكْثِرُ الْقِنَاعَ حَتَّى كَأَنَّ ثَوْبَهُ، ثَوْبُ زَيَّاتٍ‏.‏