The surah can be divided into the following three sections:
SECTION I (1-8)
The Prophet (sws) has been comforted that he should not pay any heed to the stubborn and obstinate people who are demanding to see the doom they have been promised. The greatest of signs shall not induce them to accept faith, because they do not follow the norms of sense and reason; instead they are the followers of their whims and desires. The tales of various nations should be a big lesson for them, but alas! they do not have the ability to learn from history. The Prophet (sws) is further consoled that they will not pay heed to his Message; he should leave their matter to the summoner who, on the Day of Judgement shall be summoning them not to the Quran but to hell. They shall respond to his call, emerging from their graves like locusts scattered about.
SECTION II (9-42)
The Quraish have been directed to learn a lesson from the fate of the people of Noah, Aad, Thamud, Lot and Pharoah. These people, like the Quraish, rejected their respective prophets, and if the Quraish also follow their footsteps, they will meet a similar fate. They must bear in mind that the Almighty has revealed the Quran to warn them of this danger beforehand by making it very appropriate for admonition. Instead of acknowledging this favour of the Almighty and benifitting from it, alas! it is their extreme misfortune that they are asking for punishment.
SECTION III (43-55)
The Quraish have been cautioned that when in the past the Almighty has never spared the unbelievers, they should not consider themselves an exception to this rule. Do they reckon that the Almighty has written a directive of acquittal for them in the Hereafter in the heavenly scriptures, and do they think that they shall be able to defend themselves against Allah in the Hereafter? If they have such foolish ideas, they must remember that the Almighty shall never treat the unbelievers and the righteous equally. The unbelievers shall encounter the raging fire of hell and the righteous shall dwell in the eternal bliss of paradise.
(Translated from Islahi's "Tadabbur-i-Quran") ---Shehzad Saleem