Prohibition on Speaking without Knowledge.
Al-Kāfi|Volume 1|Book 2|Chapter 11
5ـ مُحَمَّدُ بْنُ إِسْمَاعِيلَ عَنِ الْفَضْلِ بْنِ شَاذَانَ عَنْ حَمَّادِ بْنِ عِيسَى عَنْ رِبْعِيِّ بْنِ عَبْدِ الله عَنْ مُحَمَّدِ بْنِ مُسْلِمٍ عَنْ أَبِي عَبْدِ الله (عَلَيْهِ السَّلام) قَالَ لِلْعَالِمِ إِذَا سُئِلَ عَنْ شَيْءٍ وَهُوَ لا يَعْلَمُهُ أَنْ يَقُولَ الله أَعْلَمُ وَلَيْسَ لِغَيْرِ الْعَالِمِ أَنْ يَقُولَ ذَلِكَ.
5. Muhammad ibn ‘Isma’il has narrated from al-Fadl ibn Shadhan from Hammad ibn ‘Isa from Ri’ab‘i ibn ‘Abdallah from Muhammad ibn Muslim from abu ‘Abdallah عليه السلام who has said the following. “It is very proper for a scholar to say, ‘Allah knows best’ if he does not know. This is not for a none scholar.”
- Mirʾāt al-ʿUqūl fī Sharḥ Akhbār Āl al-Rasūl (1/138)
- Ṣaḥīḥ al-Kāfī, vol. 1, pp. 5, 6