Narrated 'Amr bin Shu'aib:
from his father, from his grandfather: "The Prophet (ﷺ) prohibited plucking gray hair. And he said: "It is the Muslim's light.'" (IT)
English reference (IT): Vol. 5, Book 41, Hadith 2821 (IT)
Arabic reference (IT): Book 43, Hadith 3053 (IT)