Al-Kāfi
Hadith 14192ـ عَنْهُ عَنْ عَبْدِ الله بْنِ مُسْكَانَ عَنْ أَبِي الْعَبَّاسِ قَالَ سَأَلْتُ أَبَا عَبْدِ الله (عَلَيهِ السَّلام) عَنْ أَدْنَى مَا يَكُونُ بِهِ الإنْسَانُ مُشْرِكاً قَالَ فَقَالَ مَنِ ابْتَدَعَ رَأْياً فَأَحَبَّ عَلَيْهِ أَوْ أَبْغَضَ عَلَيْهِ.
2. It is narrated from him (narrator of the Hadith above) from ‘Abd Allah ibn Muskan from abu al-‘Abbas who has said the following: “Once I asked Abu ‘Abdillah (a.s.) about the minimum degree of al-Shirk (paganism). The Imam said, ‘It is one’s inventing an opinion and thereafter love and hate (people) on that basis.’”