حَدَّثَنِي عَنْ مَالِكٍ، عَنْ يَحْيَى بْنِ سَعِيدٍ، أَنَّ أَبَا قَتَادَةَ الأَنْصَارِيَّ، قَالَ لِرَسُولِ اللَّهِ صلى الله عليه وسلم إِنَّ لِي جُمَّةً أَفَأُرَجِّلُهَا فَقَالَ رَسُولُ اللَّهِ صلى الله عليه وسلم ‏"‏ نَعَمْ وَأَكْرِمْهَا ‏"‏ فَكَانَ أَبُو قَتَادَةَ رُبَّمَا دَهَنَهَا فِي الْيَوْمِ مَرَّتَيْنِ لِمَا قَالَ لَهُ رَسُولُ اللَّهِ صلى الله عليه وسلم ‏"‏ وَأَكْرِمْهَا ‏"‏ ‏.‏

Yahya related to me from Malik from Yahya ibn Said that AbuQatada al-Ansari said to the Messenger of Allah, may Allah bless himand grant him peace, "I have a lot of hair which comes down to myshoulders, shall I comb it?'' The Messenger of Allah. may Allah blesshim and grant him peace, said, "Yes, and honour it." Sometimes AbuQatada oiled it twice in one day because the Messenger of Allah, mayAllah bless him and grant him peace, said to him. "Honour it." Translation Not Available

Book reference: Muwatta Imam Malik Book 51 Hadith 1738
Web reference: Muwatta Imam Malik Book 51 Hadith 6