Al-Kāfi - Volume 1 > Chapter on the minimum degree of knowledge of the existence of Allah
Hadith #1

1ـ مُحَمَّدُ بْنُ الْحَسَنِ عَنْ عَبْدِ الله بْنِ الْحَسَنِ الْعَلَوِيِّ وَعَلِيُّ بْنُ إِبْرَاهِيمَ عَنِ الْمُخْتَارِ بْنِ مُحَمَّدِ بْنِ الْمُخْتَارِ الْهَمْدَانِيِّ جَمِيعاً عَنِ الْفَتْحِ بْنِ يَزِيدَ عَنْ أَبِي الْحَسَنِ (عَلَيْهِ السَّلام) قَالَ سَأَلْتُهُ عَنْ أَدْنَى الْمَعْرِفَةِ فَقَالَ الاقْرَارُ بِأَنَّهُ لا إِلَهَ غَيْرُهُ وَلا شِبْهَ لَهُ وَلا نَظِيرَ وَأَنَّهُ قَدِيمٌ مُثْبَتٌ مَوْجُودٌ غَيْرُ فَقِيدٍ وَأَنَّهُ لَيْسَ كَمِثْلِهِ شَيْ‏ءٌ.

1. Muhammad ibn al- Hassan has narrated from ‘Abdallah ibn al-Hassan al-‘Alawi and Ali ibn Ibrahim from al-Mukhtar ibn Muhammad ibn al-Mukhtar al-Hmadini altogether from al- Fath ibn Yazid who has said the following. “I asked Imam abul Hassan (a.s.), “What is the minimum required degree of knowledge about Allah?” The Imam said, “To acknowledge that there is no other lord besides Him and that nothing is similar to and like Him and that He is eternal, positively existing and not absence and that nothing is like Him.”