Al-Kāfi

Hadith 1009
major-sinsrepentance
19ـ يُونُسُ عَنْ إِسْحَاقَ بْنِ عَمَّارٍ قَالَ قُلْتُ لأبِي عَبْدِ الله (عَلَيهِ السَّلام) الْكَبَائِرُ فِيهَا اسْتِثْنَاءُ أَنْ يَغْفِرَ لِمَنْ يَشَاءُ قَالَ نَعَمْ.
19. Yunus has narrated from Ishaq ibn ‘ Ammar who has said the following: “Once I asked Abu ‘Abdillah (a.s.) ‘Does the exception apply to the major sins and Allah may chose to forgive (whichever He may so choose)?’ The Imam said, ‘Yes, it does apply.’”
Source: Shaykh Muḥammad b. Yaʿqūb al-Kulaynī