Overall meaning : This surah opens with the ‘disconnected letters’ to establish the miraculous nature of the Qur’an, which conclusively prove the Arabs’ total inability to challenge the Qur’an by producing something like it, even though it is composed of the very Arabic letters they speak!
The Almighty then says: Do people think that they will be left to say, ‘We believe,’ without being tested?! We did test those before them to reveal in practice, what is already known to Us, the reality of those who truthfully live up to their faith after being put to the test and that of those who falsely claim to profess faith. Or do those who commit evil deeds think that they can escape Our punishment? What a bad judgement they make and what an erroneous belief they hold!
Next, He strikes a note of reassurance that brings the believers joy and happiness: Whoever looks forward with hope to meeting Allah on the Resurrection Day must know that the resurrection and the Day of Judgement will inevitably take place. Allah alone is the All-Hearing, All-Knowing, and He will judge and repay people according to their actions. Whoever strives hard to do what Allah commands and shun what He forbids only does so for his own good. Surely Allah is rich beyond need any of His creation. As for those who believe and do righteous deeds, We will surely erase their bad deeds and not take them to task for them, and We will reward them according to their best actions.