Sunan an-Nasa'i, Hadith 5081 ⓘ
It was narrated that 'Abdullah bin Buraidah said: "The Messenger of Allah [SAW] said: 'The best things with which you can change gray hair are Henna and Katam.'"
أَخْبَرَنَا حُمَيْدُ بْنُ مَسْعَدَةَ، قَالَ حَدَّثَنَا عَبْدُ الْوَارِثِ، قَالَ حَدَّثَنَا الْجُرَيْرِيُّ، عَنْ عَبْدِ اللَّهِ بْنِ بُرَيْدَةَ، قَالَ قَالَ رَسُولُ اللَّهِ صلى الله عليه وسلم " إِنَّ أَحْسَنَ مَا غَيَّرْتُمْ بِهِ الشَّيْبَ الْحِنَّاءُ وَالْكَتَمُ " .
also referenced under: Book 48, Hadith 42 (In-Book) & Volume 6, Book 48, Hadith 5084 (DarusSalam)