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.'" (AR)
English reference (AR): Vol. 5, Book 41, Hadith 2821 (AR)
Arabic reference (AR): Book 43, Hadith 3053 (AR)