Prohibition on Speaking without Knowledge and Ruling based on Opinion

5. [5/39] al-Kafi: Ali b. Ibrahim from Ahmad b. Muhammad b. Khalid from Hammad b. Isa from Hariz b. Abdallah from Muhammad b. Muslim from Abi Abdillah عليه السلام who said: if a man from among you is asked about that which he does not know – he should say: “I do not know” and should not say: “Allāh is more knowing”, because that will cast doubt in the heart of the questioner, and if the questioned says: “I do not know” then the questioner should not blame him.