Al-Kāfi
Hadith 142عَلِيُّ بْنُ إِبْرَاهِيمَ عَنْ أَبِيهِ عَنِ النَّوْفَلِيِّ عَنِ السَّكُونِيِّ عَنْ أَبِي عَبْدِ اللَّهِ ( عليه السلام ) قَالَ قَالَ أَمِيرُ الْمُؤْمِنِينَ ( عليه السلام ) إِذَا أَسْلَمَ الرَّجُلُ اخْتَتَنَ وَ لَوْ بَلَغَ ثَمَانِينَ .
10. Ali ibn Ibrahim has narrated from his father from al-Nawfaliy from al-Sakuniy who has said the following: “Abu ‘Abd Allah (a.s.), has said that ’Amir al-Mu’minin has said, ‘If a man becomes a Muslim he must circumcise even if he is eighty years old.’”