The Surah takes its name from the word al-waqi\`ah of the very first verse.
According to the chronological order that Hadrat Abdullah bin Abbas has given of the Surahs, first Surah Ta Ha was sent down, then Al-Waqi'ah and then Ash-Shu\`ara'(Suyuti: Al-Itqan). The same sequence has been reported from Ikrimah (Baihaqi: Dala'il an Nubuwwat).
This is supported also by the story that Ibn Hisham has related from Ibn Ishaq about the affirmation of the Faith by Hadrat Umar (may Allah be pleased with him). It says that when Hadarat Umar entered his sister's house, Surah Ta Ha was being recited. Hearing his voice the people of the house hid the pages of the Qur'an. Hadrat Umar first seized his brother-in-law and then his sister rose in defense of her husband, he hit her also and wounded her on the head. When Umar saw blood on his sister, he was sorry for what he had done, and said to her: "Show me the manuscript that you have concealed so that I may see what it contains." The sister said: "You are unclean because of your polytheism: wa anna-hu la yamassu-ha ill-at-tahir : "Only a clean person can touch it." So, Hadrat Umar rose and washed himself, and then took up the manuscript to read it. This shows that Surah Al-Waqi'ah had been sent down by that time for it contains the verse: La yamassu hu ill al mutahharun ; and it had been established historically that Hadrat Umar embraced Islam after the first migration to Habash, in the fifth year of the Prophethood.
Its theme is the Hereafter, Tauhid and refutation of the Makkan disbelievers' suspicions about the Qur'an. What they regarded as utterly incredible was that Resurrection would ever take place, then the entire system of the earth and heavens would be upset, and when all the dead would be resurrected and called to account, after which the righteous would be admitted to Paradise and the wicked cast into Hell. They regarded all this as imaginary, which could not possibly happen in actual fact. In answer to this, it was said: "When the inevitable event will take place, there will be none to belie its happening, nor will anyone have the Power to avert it, nor prove it to, be an unreal happening. At that time all peoples will be divided into three classes: (1) The foremost in rank and position; (2) the common righteous people and (3) those who denied the Hereafter and persisted in disbelief and polytheism and major sins till the last." How these three classes of the people will be rewarded and punished has been described in detail in vv. 7-56.
Then, in vv. 57-74 arguments have been given, one after the other, to prove the truth of the two basic doctrines of Islam, which the disbelievers were refusing to accept, viz. the doctrines of Tauhid and the Hereafter. In these arguments, apart from every thing else that exists in the earth and heavens, man's attention has been drawn to his own body and to the food that he eats and to the water that he drinks and to the fire on which he cooks his food, and he has been invited to ponder the question : What right do you have to behave independently of, or serve any other than, the God Whose creative power has brought you into being, and Whose provisions sustain you And how can you entertain the idea that after having once brought you into existence He has become so helpless and powerless that He cannot recreate you once again even if he wills to?
Then, in vv. 75-82 their suspicions in respect of the Qur'an have been refuted and they have been made to realize how fortunate they are that instead of deriving any benefit from the great blessing that the Qur'an is, they are treating it with scant attention and have set only this share of theirs in it that they deny it. If one seriously considers this matchless argument that has been presented in two brief sentences about the truth of the Qur'an, one will find in it the same kind of firm and stable system as exists among the stars and planets of the Universe, and the same is the proof of the fact that its Author is the same Being Who has created the Universe. Then the disbelievers have been told that this Book is inscribed in that Writ of Destiny which is beyond the reach of the creatures, as if to say "You think it is brought down by the devils to Muhammad (peace and blessings of Allah be upon him), whereas none but the pure angels has any access to the means by which it reaches Muhammad (peace and blessings of Allah be upon him) from the well guarded Tablet."
In conclusion, man has been warned, as if to say: "You may brad and boast as you like and may shut your eyes to the truths in your arrogance of independence, but death is enough to open your eyes. At death you become helpless: you cannot save your own parents; you cannot save your children; you cannot save your religious guided and beloved leaders. They all die in front of your vary eyes while you look on helplessly. If there is no supreme power ruling over you, and your this assumption is correct that you are all in all in the world, and there is no God, then why don't you restore to the dying person his soul?Just as you are helpless in this, so it is also beyond your power to stop Allah from calling the people to account and mete out rewards and punishments to them. You may or may not believe it, but every dying person will surely see his own end after death. If he belongs to those nearest to God, he will see the good end meant for them if he be from among the righteous, he will see the end prepared for the righteous; and if he be from among the deniers of the truth, he will see the end destined for the criminals.
Source: Sayyid Abul Ala Maududi - Tafhim al-Qur'an - The Meaning of the Quran