Al-Kāfi - Volume 1 > The Case of those who would Die without having an Imam from the Imams of Guidance
Hadith #4

4ـ بَعْضُ أَصْحَابِنَا عَنْ عَبْدِ الْعَظِيمِ بْنِ عَبْدِ الله الْحَسَنِيِّ عَنْ مَالِكِ بْنِ عَامِرٍ عَنِ الْمُفَضَّلِ بْنِ زَائِدَةَ عَنِ الْمُفَضَّلِ بْنِ عُمَرَ قَالَ قَالَ أَبُو عَبْدِ الله (عَلَيْهِ السَّلام) مَنْ دَانَ الله بِغَيْرِ سَمَاعٍ عَنْ صَادِقٍ أَلْزَمَهُ الله الْبَتَّةَ إِلَى الْعَنَاءِ وَمَنِ ادَّعَى سَمَاعاً مِنْ غَيْرِ الْبَابِ الَّذِي فَتَحَهُ الله فَهُوَ مُشْرِكٌ وَذَلِكَ الْبَابُ الْمَأْمُونُ عَلَى سِرِّ الله الْمَكْنُونِ.

4. Certain persons of our people have narrated from ‘Abd al-‘Azim ibn ‘Abdallah al-Hassani from Malik ibn ‘Amir from al-Mufaddal ibn Za’id from al-Mufaddal ibn ‘Umar who has said the following. “Abu ‘Abdallah (a.s.) has said, ‘Whoever would follow the religion of Allah without hearing (instructions) from a truthful (Imam) person Allah will cause him, inevitably, to suffer hardships. Whoever would claim to have heard from a source other than the one Allah has opened for him, he will be considered as polytheist. The source and door that Allah has opened is the one that trustworthy in the matters of the hidden secrets of Allah.”