Al-Kāfi

Hadith 1403
disbelief
15ـ مُحَمَّدُ بْنُ يَحْيَى عَنْ أَحْمَدَ بْنِ مُحَمَّدٍ عَنِ ابْنِ مَحْبُوبٍ عَنْ أَبِي أَيُّوبَ عَنْ مُحَمَّدِ بْنِ مُسْلِمٍ قَالَ سَمِعْتُ أَبَا جَعْفَرٍ (عَلَيهِ السَّلام) يَقُولُ كُلُّ شَيْ‏ءٍ يَجُرُّهُ الإقْرَارُ وَالتَّسْلِيمُ فَهُوَ الإيمَانُ وَكُلُّ شَيْ‏ءٍ يَجُرُّهُ الإنْكَارُ وَالْجُحُودُ فَهُوَ الْكُفْرُ.
15. Muhammad ibn Yahya has narrated from Ahmad ibn Muhammad from ibn Mahbub from abu Ayyub from Muhammad ibn Muslim who has said the following: “I heard abu Ja’far (a.s.) saying, ‘Anything that professing and submission carry is belief, and anything that denial and rejection carry is disbelief.’”
Source: Shaykh Muḥammad b. Yaʿqūb al-Kulaynī