Summary
The Resurrection and the Day of Judgement are of paramount importance in Islam, they are part of the culimination of this life in the sense that everything that is done upon this Earth will be judged and then justice will be served upon every individual. It is something that gives hope and fear at the same time, hope as there will be complete justice done, so if anyone opressed another person on this Earth and seemingly got away with it, they will ultimately be answerable for it, and fear for the one who has disobeyed God and performed evil acts.
How can you disbelieve in Allah when you were lifeless and He brought you to life; then He will cause you to die, then He will bring you [back] to life, and then to Him you will be returned. [The Qur'an:al-Baqarah 2:28]
“And fear a Day when you will be returned to Allah . Then every soul will be compensated for what it earned, and they will not be treated unjustly.” [The Qur'an: al-Baqarah 2:281]
That Day, the people will depart separated [into categories] to be shown [the result of] their deeds. So whoever does an atom's weight of good will see it, And whoever does an atom's weight of evil will see it. [The Qur'an: al-Zalzalah 99:6-8]
Full Answer
The Resurrection and the Day of Judgement are events that will occur at the end of time when this world has ended and everyone in existence has passed away. It is the stage of the afterlife that begins after The Grave and has been mentioned in much detail in the Qur'an and the Sunnah (Traditions) of the Prophet Muhammad [May the Peace and Blessings of Allah be upon him].
The first thing to occur is the resurrection, here are some verses and narrations which describe this phase:
And the Horn will be blown; and at once from the graves to their Lord they will hasten. [The Qur'an: Ya-Sin 36:51]
“As We began the first creation, We shall repeat it,” [The Quran Al-Anbiyaa’ 21:104]
The Prophet Muhammad (May the Peace and Blessings of Allah be upon him) said:
The Earth would consume every son of Adam except his spinal chord from which his body would be resurrected (on the Day of Resurrection). [Sahih Muslim 2955 b]
The Prophet Muhammad (May the Peace and Blessings of Allah be upon him) said:
“Then (after this period) Allah will send water from the sky and then the dead bodies will grow like vegetation grows. “ [Sahih Muslim 2955]
After being resurrected, the people will proceed to the place of judgement. It is mentioned in a hadith (narration) that the place of judgement is Shaam (Shaam is an area which comprises Palestine and Syria):
The Prophet (May the Peace and Blessings of Allah be upon him) said: “Al-Shaam is the land of the gathering and the resurrection.” [Narrated by Ahmad]
There are many verses and narrations regarding what will happen on the Day of Judgement, it is mentioned that the day itself will be the length of 50,000 years:
The angels and the Spirit will ascend to Him during a Day the extent of which is fifty thousand years. [The Qur'an Al-Ma'arij 70:4]
Although the Day of Judgement is extremely long, it is mentioned that for the righteous believer, it will be like the time between the mid day prayer and the afternoon prayer (i.e a few hours):
The Prophet (May the Peace and Blessings of Allah be upon him) said: “For the believers, the (length of) the Day of Resurrection will be like the time between Dhuhr and ‘Asr.” [Reported by al-Haakim in al-Mustadrak, Saheeh al-Jaami’, 8193]
Muslims are told to remember the Day of Judgement often as it reminds them that everything they do will be asked about on that day, and if they have committed any injustice towards anyone they will be accountable for it.
“Every soul will taste death, and you will only be given your [full] compensation on the Day of Resurrection. So he who is drawn away from the Fire and admitted to Paradise has attained [his desire]. And what is the life of this world except the enjoyment of delusion.” [The Quran: An-Nisaa’ 3:185]
“And fear a Day when you will be returned to Allah . Then every soul will be compensated for what it earned, and they will not be treated unjustly.” [The Qur'an: al-Baqarah 2:281]
When being judged a person’s good deeds and bad deeds are balanced in a scale as mentioned in the following verse:
“Then as for one whose scales are heavy [with good deeds], He will live a pleasant life (in Paradise). But as for one whose scales are light, He will have his home in Hawiyah (pit, i.e. Hell).” [The Quran: al-Qaariah 101: 6-9]
Muslims believe that the first thing that they will be asked about on the Day of Judgement is the prayer, this is due to the narration of the Prophet Muhammad (May the Peace and Blessings of Allah be upon him):
“The first matter that the slave will be brought to account for on the Day of Judgment is the prayer. If it is sound, then the rest of his deeds will be sound. And if it is bad, then the rest of his deeds will be bad.” [Sunan an-Nasa'i 467]
It is also mentioned that before being allowed to move, five things will be asked:
The Prophet Muhammad (May the Peace and Blessings of Allah be upon him) said, “Man's feet will not move on the Day of Resurrection before he is asked about his life, how did he consume it, his knowledge, what did he do with it, his wealth, how did he earn it and how did he dispose of it, and about his body, how did he wear it out.” [At-Tirmidhi Book 1, Hadith 407]
Even the smallest of details from a persons life will be brought out in front of them, it is mentioned how people will be amazed by this in the Qur'an:
“And the record [of deeds] will be placed [open], and you will see the criminals fearful of that within it, and they will say, “Oh, woe to us! What is this book that leaves nothing small or great except that it has enumerated it?” And they will find what they did present [before them]. And your Lord does injustice to no one.” [The Qur'an: al-Kahf 18:49]
The Day of Judgement ends with a person being chosen for either Paradise or the Hell Fire and they are then transported to their destinations. For the people of Paradise Allah says in the Qur'an:
And Paradise will be brought near to the righteous, not far, , “This is what you were promised – for every returner [to Allah ] and keeper [of His covenant] Who feared the Most Merciful unseen and came with a heart returning [in repentance]. Enter it in peace. This is the Day of Eternity.” [The Qur'an: Qaf 50:32-34]
And for the people of Hell-fire:
“[It will be commanded], “Seize him and drag him into the midst of the Hellfire,” [The Qur'an: al-Dukhaan 44:47]
In summary, the Day of Judgement is a day which is always on the mind of a Muslim, it makes them consider the righteouness of every single action that they do in their life in preperation for when they will be judged as is mentioned by Allah in the Qur'an:
That Day, the people will depart separated [into categories] to be shown [the result of] their deeds. So whoever does an atom's weight of good will see it, And whoever does an atom's weight of evil will see it. [The Qur'an: al-Zalzalah 99:6-8]
