Al-Kāfi - Volume 6 > Clipping or Pulling out Gray Hairs
Hadith #5

عَلِيُّ بْنُ إِبْرَاهِيمَ عَنْ أَبِيهِ عَنِ ابْنِ أَبِي عُمَيْرٍ عَنْ حَفْصِ بْنِ الْبَخْتَرِيِّ عَنْ أَبِي عَبْدِ اللَّهِ ( عليه السلام ) قَالَ كَانَ النَّاسُ لَا يَشِيبُونَ فَأَبْصَرَ إِبْرَاهِيمُ ( عليه السلام ) شَيْباً فِي لِحْيَتِهِ فَقَالَ يَا رَبِّ مَا هَذَا فَقَالَ هَذَا وَقَارٌ فَقَالَ يَا رَبِّ زِدْنِي وَقَاراً .

5. Ali ibn Ibrahim has narrated from his father from ibn abu ‘ Umayr from Hafs ibn al-Bakhtariy who has said the following: “Abu ‘Abd Allah, ‘Alayhi al-Salam, has said, ‘People did not grow gray hairs but Ibrahim ‘Alayhi al- Salam, found gray in his beard and asked, ‘O Lord, what is this?’ He said, ‘It is reverence.’ He then said, ‘O Lord, increase my reverence.’”