Al-Kāfi - Volume 6 > Clipping or Pulling out Gray Hairs
Hadith #2

عَنْهُ عَنِ ابْنِ فَضَّالٍ عَمَّنْ ذَكَرَهُ عَنْ أَبِي عَبْدِ اللَّهِ ( صلوات الله عليه ) قَالَ لَا بَأْسَ بِجَزِّ الشَّمَطِ وَ نَتْفِهِ مِنَ اللِّحْيَةِ .

2. It is narrated from the narrator of the previous Hadith from ibn Faddal from those whom he has mentioned who has said the following: “Abu ‘Abd Allah, ‘Alayhi al-Salam, has said, ‘It is not unlawful to pull up or clip gray from the beard.’”