Messenger of Allah ﷺ said, "The Jews and the Christians do not dye (their grey hair), so you shall do the opposite of what they do (i.e. dye your grey hair and beards). (Using translation from Bukhārī 3462)

قَالَ رَسُولُ اللَّهِ ﷺ «إِنَّ الْيَهُودَ وَالنَّصَارَى لَا يَصْبِغُونَ فَخَالِفُوهُمْ»