He heard that the Messenger of Allah [SAW] said: "The best things with which you can change gray hair are Henna and Katam." (Using translation from Nasāʾī 5082)
أَنَّ رَسُولَ اللهِ ﷺ قَالَ «إِنَّ أَحْسَنَ مَا غُيِّرَ بِهِ الشَّيْبُ الْحِنَّاءُ وَالْكَتَمُ»