Overall meaning :
The surah begins with the ‘disconnected letters’ which establish the miraculous nature of the Qur’an and 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: These are the verses of the clear Qur’an, which makes the truth manifest.
Then He addresses His Messenger, may Allah bless him and grant him peace, comforting him as he faces the idolaters’ vehement denial of his message: Perhaps you will torment yourself to death with grief and sorrow because of the unbelievers’ rejecting you and stubbornly refusing to believe in your call. Had We willed, We would have sent down to these unbelievers a visible miraculous sign from the heavens that would compel them to believe, and so they would submit to the truth by force, but, in Our wisdom, We have willed that everyone’s faith be voluntary.
Next, He points out these unbelievers’ persistent denial of the truth and the terrible consequences they will suffer as a result of such denial: Whenever a fresh revelation of the Qur’an comes to you, Messenger, they turn their backs on it and do not believe in it. They have denied the Qur’an that has come down to them from Allah, so they will soon come to know the truth of what they mock and will face the consequences of their denying the truth.
The Almighty then reproves them for neglecting to contemplate this universe: Do they not see the earth and reflect on the countless types of pleasant and wholesome plants that We have caused to grow in it? Surely in this there is a sign of Allah’s perfect power; yet most of these idolaters would not believe. And surely your Lord, Muhammad, is the Almighty who vanquishes and severely punishes His enemies, and the All-Compassionate towards His servants, who does not hasten their punishment once they commit a sin.