The early Muslim believers of Mecca lived in turmoil especially at the beginning period of Islam. They were always faced with torture; bodily and spiritually, by the pagan Arabs who forced them to leave their Faith. Some of them, the weak ones, succumbed, but, the stonger ones resisted.
This is a Meccan Sura whose main objective seems to be the spiritual strengthening of the believers against that process, and encouraging them to persevere.
Concerning this point, it tells the story of 'the makers of the pit of fire', those who dug some ditches in which they burnt people for their Faith. They threatened them and burnt them, but the true believers did not loose their Faith.
In another section of the Sura, the pagans are threatened with the blazing fire of Hell for the persecution of Allah's votaries, while the believers are given good news about the gardens of Bliss.
Then, to attract their attention to past generations, it illustrates the story of Pharaoh, the people of Thamud and some other arrogant sects. They lived in such great authority, in the past, that the pagans of Mecca were naught in comparison with them, but they could not stand for Allah's command and perished. Besides, these examples are for soothing the heart of the Prophet (p.b.u.h.) and of the believers.
Finally, the Sura ends with an explanation about the greatness and the extraordinary importance of the Holy Qur'an.
On the whole, this is a Sura of resistant perseverance, and patience from the side of the believers against the persecutions of the enemies, amongst which the promise of Allah's victory is found.
The name of the Sura is taken from the oath which occurred in the beginning verse of the Sura.
The Virtue in Studying this Sura:
There is a tradition from the Prophet (p.b.u.h.) for the virtue of this Sura which says: Allah will give reward for the good-deeds ten times the number of all people gathered in 'Friday Prayer' and all people gathered on the day of 'Arafah (the ninth day of Zilhajj), to the person who studies this Sura. Its recitation saves Man from fears.
These rewards fit in with the content of the Sura and it is obvious when we consider that: one of the commentaries for the verse: By the Witness and the Witnessed is 'Friday' and Arafah Day', and that the Sura denotes to the severe perseverance of the early believers against the enemies' persecutions. By the way, it also confirms that these rewards belong to those who study the Sura, then contemplate on it and act accordingly.