[40].Surah Al Mumin (The Believer) also known as Surah Ghafir [The Forgiver]: Ayat 083

৮৩. তাদের কাছে যখন তাদের রসূলগণ স্পষ্ট প্রমাণাদিসহ আগমন করেছিল, তখন তারা নিজেদের জ্ঞান-গরিমার দম্ভ প্রকাশ করেছিল। তারা যে বিষয় নিয়ে ঠাট্টাবিদ্রুপ করেছিল, তাই তাদেরকে গ্রাস করে নিয়েছিল।

Ayat 83. Then when their Messengers came to them with clear proofs, they were glad (and proud) with that which they had of the knowledge (of worldly things): And that at which they used to mock, surrounded them (i.e. the punishment).

Tafseer of Surah Al Mumin (The Believer) 83. For when their messengers came to them with Clear Signs, they exulted in such knowledge (and skill) as they had; but that very (Wrath) at which they were won’t to scoff hemmed them in. Arrogance and an exaggerated idea of Self were at the bottom of the Evil to which they succumbed Cf. 16:34 . Nothing could stop the Justice of Allah punishing Evil. What they had ridiculed came as an inexorable fact. None of their grandeur or art or science or skill was of any use when they lost their souls! 

Hazrat Masruq (May Allah be pleased with him) said: We visited `Abdullah bin Masud (May Allah be pleased with him) and he said to us: O people! He who has the knowledge of any matter may convey it to the others. And he who has no knowledge, thereof, should say: "Allahu a'lam (Allah knows better).'' It is a part and parcel of knowledge that a man who has no knowledge of a matter should say: "Allah knows better.'' Allah said to His Prophet [SAWW](PBUH): "Say (O Muhammad [SAWW](PBUH)): `No wage do I ask of you for this (the Qur'an), nor am I one of the Mutakallifun (those who pretend and fabricate things which do not exist).''' (38:86)

[Al-Bukhari Book 06, Chapter 60, Hadith # 333].

Lesson: as mentioned above in Surah Al-Mumin Ayat 83. “they were glad (and proud) with that which they had of the knowledge (of worldly things)”  If one does not know about something, he should not say anything about it by way of conjecture, speculation and guesswork because this is also pretension which is forbidden. When religious scholars are asked about anything which they do not know, they should confess their ignorance. Such a confession is also a mark of scholarship. In other words, they should abstain from giving verdict about any matter without making a thorough study and research on it.