Mukhtasar Muslim (Abridged) 1348 — Opposing Jews and Christians

Narrated from Sayyiduna Abu Hurairah (may Allah be pleased with him) that the Noble Prophet (peace and blessings of Allah be upon him) said: The Jews and Christians do not dye (their hair), so you should do the opposite of them (i.e., dye your hair, but as mentioned in the previous hadith, not with black dye).