The explanation of Chapter Az-Zalzalah (The Earthquake)

From: http://www.islamweb.net/ver2/archive/article.php?lang=E&id=156535

Text:
In the Name of Allaah, the Most Beneficent, the Most Merciful
1. When the earth is shaken with its [final] earthquake
2. And the earth discharges its burdens
3. And man says, "What is wrong with it?" -
4. That Day, it will report its news
5. Because your Lord has inspired [i.e. commanded] it
6. That Day, the people will depart separated [into categories], to be shown [the result of] their deeds
7. So whoever does an atom's weight of good will see it,
8. And whoever does an atom's weight of evil will see it.

Explanation:
"When the earth is shaken with its [final] earthquake"
Ibn 'Abbaas said that it means: "When the earth moves from beneath its surface."
"And the earth discharges its burdens"
That is, when it throws out its dead. This is said by many, like the Words of Allaah (which mean):"O mankind, fear your Lord. Indeed, the convulsion of the [final] Hour is a terrible thing."[Quran 22:1], and:
"And when the earth has been extended, and has cast out that within it and relinquished [it]." [Quran 84:3-4] It is narrated on the authority of Abu Hurayrah that the Messenger of Allaah said: "The earth will throw out what is hidden within it, such as columns of gold and silver, and the murderer will say: 'For this I committed murder.' Then the one who severed family ties will say: 'For this I severed relations.' Then the thief will come and say: 'For this was my hand cut.' Then they will leave it and not take anything from it."[Muslim and At-Tirmithi]

"And man says, 'What is wrong with it?'" -
That is, in bewilderment, he cries out: "What is happening to the earth, which previously was fixed, firm and peaceful and is now moving in convulsions under its surface?" It does so by the Command of Allaah, the Most High. Then it throws out all of its dead from the first generation to the last, and at this time man cries out in astonishment: "What is wrong with it?"

"That Day, it will report its news"
That is, it will speak about the actions of those whom it has thrown forth. It is narrated on the authority of Abu Hurayrah that he said: "The Messenger of Allaah read the verse (which means): "That Day, it will report its news," then he said: "Do you know what the news are?" We (the listening companions) replied: "Allaah and His Messenger know best." He said: "Verily, (they) are that it will testify concerning every slave, male and female, about what they did on its surface, that it will say: 'He did this and this on such-and-such a day.' - Those are its news." [Imaam Ahmad]

"Because your Lord has inspired [i.e. commanded] it"
Mujaahid said it means that Allaah will command the earth to give its tidings.
"That Day, the people will depart separated [into categories], to be shown [the result of] their deeds,"
That is, they will proceed to the place of reckoning in scattered groups, according to their type, ranging from the most abjectly wretched to the joyful, having been ordered to proceed to Hell or Paradise.

"to be shown [the result of] their deeds".
To confirm what they did in their earthly life, whether good or bad, as Allaah says (what means):

"So whoever does an atom's weight of good will see it, and whoever does an atom's weight of evil will see it."
It is narrated on the authority of 'Adiy Ibn Haatim that the Messenger of Allaah said: "Fear the Fire even if it were by (giving) a portion of a date or by (saying) a good word. Do not despise any act of kindness, even if it were to fill the drinking vessel of a thirsty person from your bucket, or to meet your brother face-to-face and smile at him." [Al-Bukhaari]
Also narrated by Al-Bukhaari is: "O community of believing women! Let not the woman neighbour despise her woman neighbour, even if it were by (giving her) a sheep's trotter." In another authentic narration, he said: "Respond to the one who asks (for assistance) even if it were with only a burnt trotter." It is narrated on the authority of 'Amr Ibn Al-'Aas that he said: "When the Soorah (Quranic chapter), "When the earth is shaken with its [final] earthquake" was revealed, Abu Bakr who was sitting with the Prophet began to cry. The Messenger of Allaah asked him: "What makes you cry, O, Abu Bakr?" Abu Bakr replied: 'This Soorah makes me cry.' Then the Messenger of Allaah said: "Even if you did not err and commit sins that Allaah might forgive you, He would have created another community who erred and committed sins that He might forgive them."[Muslim]
"So whoever does an atom's weight…" That is, the most insignificant weight - less than an ant.
"… of good will see it."
That is, he shall see it recorded in the book given to him on the Day of Judgment, and he will be pleased with that: Every sinful act, every charitable deed is recorded therein. Every bad deed will be recompensed as one deed, while every good deed will be recompensed ten times over. Whoever has more good deeds than bad will enter Paradise.
The Messenger of Allaah said:
"Beware of the minor sins, because they will build up over a man until they destroy him." [Ahmad]
Anas said: "The Messenger of Allaah said: "Say: 'He is Allaah, One." is equal to one-third of the Quran and "When the earth is shaken with its [final] earthquake" is equivalent to one-quarter of the Quran." [Al-Bazzaar] It is also reported on the authority of Anas Ibn Maalik '' that Allaah's Messenger said to a man: "Have you married, O, so-and-so?" He replied: "No, by Allaah! I have not the wherewithal, how may I marry?" The Messenger said: "…Do you not have When the earth is shaken with its [final] earthquake?" The man replied: "Certainly!" The Prophet said: "(It is) one-quarter of the Quran: Marry!" [At-Tirmithi]