It was narrated from 'Amr bin Sh'uaib from his father, that his grandfather said:
"The Messenger of Allahﷺ forbade plucking out white hairs and said: 'It is the light of the believer.'"

حَدَّثَنَا أَبُو بَكْرِ بْنُ أَبِي شَيْبَةَ، حَدَّثَنَا عَبْدَةُ بْنُ سُلَيْمَانَ، عَنْ مُحَمَّدِ بْنِ إِسْحَاقَ، عَنْ عَمْرِو بْنِ شُعَيْبٍ، عَنْ أَبِيهِ، عَنْ جَدِّهِ، قَالَ نَهَى رَسُولُ اللَّهِ ـ ﷺ ـ عَنْ نَتْفِ الشَّيْبِ وَقَالَ " هُوَ نُورُ الْمُؤْمِنِ " .