He traced it back to the Prophet ﷺ, who said, "The Jews and Christians do not dye their hair, so differ from them."
حدثنا سفيان عن الزهري عن أبي سلمة وسليمان بن يسار
يبلغ به النبي ﷺ إن اليهود والنصارى لا يصبغون فخالفوهم
Its isnad is sahih. Sulayman bin Yasar, his biography was given previously at 6189, and we add here that Ibn Abu Hatim also gave his biography in al-Jarh wal-Tadil 149/1/2, and Ibn Saad in al-Tabaqat 132/2/2, 5:13, where he said, "He was trustworthy, of high standing, eminent, a jurist, and prolific in hadith."The hadith was narrated by Bukhari 10:299 and Muslim 2:160, both of them through Sufyan bin Uyayna, with this isnad. Bukhari also narrated it, 6:361-362, through Ibrahim bin Saad from Salih from Ibn Shihab, that is Zuhri, from Abu Salama bin Abdul-Rahman alone, from Abu Hurairah.It will also come with chains of transmission through Zuhri at 7533, 8069, 9198. See also what has passed at 1415, 2470, 4672.