Often in Islamic Discussions we find people, including ourselves, give our opinions on topics that we may not have necessarily researched properly. At the conclusion of our statements, we end with “Allahu A`lam” or “Allah knows best”.. but is this correct?

Imam Baqir (as) said: “What you know you may speak about, but what you do not know say, ‘Allah knows best.’ Lo! if a person singles out any verse from Qur’ãn – the Book of Allãh (to misinterpret it) – he falls down as far away as the heaven is from the earth.”

Imam Sadiq (as) said: “If a learned man is interrogated on something he does not know, it is obligatory on him to state Allãh knows best’, but if he is not learned (and still interrogated) then he has no right even to state that much.” (that is, “Allãh knows best.”)

Imam Sadiq (as) said: “If one of you is asked about something you do not know you must say, ‘I have no knowledge,’ and you must not say, ‘Allah knows best’ because it may create doubts in the hearts of your audience. If the person questioned says, ‘I do not know’ his audience will not accuse him of anything.
Source: Usool Al-Kafi, Volume 1, Hadiths #98-100

Gradings: all narrations are reliable in chain according to the standards of al-Majlisi

In Nahjul Balagha, Imam Ali (as) says: “no one should feel ashamed of saying “I do not know” when he is asked a matter which he does not know; no one should feel ashamed of learning a thing that he does not know”

لَا يَسْتَحِيَنَّ أَحَدٌ مِنْكُمْ إِذَا سُئِلَ عَمَّا لَا يَعْلَمُ أَنْ يَقُولَ لَا أَعْلَمُ وَ لَا يَسْتَحِيَنَّ أَحَدٌ إِذَا لَمْ يَعْلَمِ الشَّيْ‏ءَ أَنْ يَتَعَلَّمَهُ


No one should be ashamed in saying “I don’t know”.. At times we give our flamboyant opinions and follow through with “Allah knows best” while we are not learned in this topic. Only when one is learned about a topic, and is faced with a question they do not completely have an answer to, they may/should say “Allah knows best”.. while for those who are not learned, they must state their ignorance lest they create doubt in the audience. Giving opinions from your own whims in itself is dangerous, as we have many hadiths warning about the danger of this.

Imam Baqir (as) said: “All the angels of divine mercy and the angels of divine wrath invoke curse for the person who pronounces verdicts regarding religious affairs before the people without having knowledge and guidance. Further such a person is liable to bear all the responsibilities of the persons who follow his wrong verdicts.” [Usool Al-Kafi, Alaamah Majlisi says it is Sahih (see hadith 3 in above image of Mira’at Al-Uqool, Volume 1, page 137)]