The doomsday ends any kinds of disagreement and falsity

The most important program of divine messengers is soul purification and effective factor of soul purification is to remember the doomsday because forgetting the doomsday and the resurrection is the greatest barrier of soul purification. Therefore, Quran gives a lot of attention to the matter of the resurrection. Persons that accept God and the source of the world deny the doomsday and say
وَأَقْسَمُوا بِاللَّهِ جَهْدَ أَيْمَانِهِمْ ۙ لَا يَبْعَثُ اللَّهُ مَن يَمُوتُ ۚ بَلَىٰ وَعْدًا عَلَيْهِ حَقًّا وَلَٰكِنَّ أَكْثَرَ النَّاسِ لَا يَعْلَمُونَ
They swear their strongest oaths by Allah, that Allah will not raise up those who die: Nay, but it is a promise (binding) on Him in truth: but most among mankind realise it not.
Quran mentions the resurrection as a day that will definitely come. It is not possible to be doubtful about the doomsday and all realities will appear there. One of reasons of the necessity of the doomsday is wisdom of God. Since God is sagacious, he never does futile actions as Quran states
وَمَا خَلَقْنَا السَّمَاوَاتِ وَالْأَرْضَ وَمَا بَيْنَهُمَا لَاعِبِينَ
We created not the heavens, the earth, and all between them, merely in (idle) sport.
Another reason is reality. Since God is true, he never does false actions. The third reason is justice. As long as there is human, there is thought. It is not true that all of persons have same thoughts, beliefs and purposes. Quran reminds the doomsday and says that God is true and reality should appear. Quran states
وَمَا أَكْثَرُ النَّاسِ وَلَوْ حَرَصْتَ بِمُؤْمِنِينَ
Yet no faith will the greater part of mankind have, however ardently thou dost desire it.
God states to the messenger of God (peace of Allah be upon him and his descendants)
وَإِن تُطِعْ أَكْثَرَ مَن فِي الْأَرْضِ يُضِلُّوكَ عَن سَبِيلِ اللَّهِ ۚ إِن يَتَّبِعُونَ إِلَّا الظَّنَّ وَإِنْ هُمْ إِلَّا يَخْرُصُونَ
Wert thou to follow the common run of those on earth, they will lead thee away from the way of Allah. They follow nothing but conjecture: they do nothing but lie .
Quran states about the doomsday
وَأَقْسَمُوا بِاللَّهِ جَهْدَ أَيْمَانِهِمْ ۙ لَا يَبْعَثُ اللَّهُ مَن يَمُوتُ ۚ بَلَىٰ وَعْدًا عَلَيْهِ حَقًّا وَلَٰكِنَّ أَكْثَرَ النَّاسِ لَا يَعْلَمُونَ
They swear their strongest oaths by Allah, that Allah will not raise up those who die: Nay, but it is a promise (binding) on Him in truth: but most among mankind realise it not.
لِيُبَيِّنَ لَهُمُ الَّذِي يَخْتَلِفُونَ فِيهِ وَلِيَعْلَمَ الَّذِينَ كَفَرُوا أَنَّهُمْ كَانُوا كَاذِبِينَ
They must be raised up), in order that He may manifest to them the truth of that wherein they differ, and that the rejecters of Truth may realise that they had indeed (surrendered to) Falsehood.
يَوْمَ تَشْهَدُ عَلَيْهِمْ أَلْسِنَتُهُمْ وَأَيْدِيهِمْ وَأَرْجُلُهُم بِمَا كَانُوا يَعْمَلُونَ
On the Day when their tongues, their hands, and their feet will bear witness against them as to their actions.
يَا أَيُّهَا الَّذِينَ آمَنُوا كُونُوا قَوَّامِينَ بِالْقِسْطِ شُهَدَاءَ لِلَّهِ وَلَوْ عَلَىٰ أَنفُسِكُمْ أَوِ الْوَالِدَيْنِ وَالْأَقْرَبِينَ ۚ إِن يَكُنْ غَنِيًّا أَوْ فَقِيرًا فَاللَّهُ أَوْلَىٰ بِهِمَا ۖ فَلَا تَتَّبِعُوا الْهَوَىٰ أَن تَعْدِلُوا ۚ وَإِن تَلْوُوا أَوْ تُعْرِضُوا فَإِنَّ اللَّهَ كَانَ بِمَا تَعْمَلُونَ خَبِيرًا
O ye who believe! stand out firmly for justice, as witnesses to Allah, even as against yourselves, or your parents, or your kin, and whether it be (against) rich or poor: for Allah can best protect both. Follow not the lusts (of your hearts), lest ye swerve, and if ye distort (justice) or decline to do justice, verily Allah is well-acquainted with all that ye do.
يَوْمَئِذٍ يُوَفِّيهِمُ اللَّهُ دِينَهُمُ الْحَقَّ وَيَعْلَمُونَ أَنَّ اللَّهَ هُوَ الْحَقُّ الْمُبِينُ
On that Day Allah will pay them back (all) their just dues, and they will realise that Allah is the (very) Truth, that makes all things manifest.
Quran states that the doomsday is true and it will come true;
ذَٰلِكَ الْيَوْمُ الْحَقُّ ۖ فَمَن شَاءَ اتَّخَذَ إِلَىٰ رَبِّهِ مَآبًا
That Day will be the sure Reality: Therefore, whoso will, let him take a (straight) return to his Lord.
The messenger of God (peace of Allah be upon him and his descendants) states
وَالَّذِينَ آتَيْنَاهُمُ الْكِتَابَ يَفْرَحُونَ بِمَا أُنزِلَ إِلَيْكَ ۖ وَمِنَ الْأَحْزَابِ مَن يُنكِرُ بَعْضَهُ ۚ قُلْ إِنَّمَا أُمِرْتُ أَنْ أَعْبُدَ اللَّهَ وَلَا أُشْرِكَ بِهِ ۚ إِلَيْهِ أَدْعُو وَإِلَيْهِ مَآبِ
Those to whom We have given the Book rejoice at what hath been revealed unto thee: but there are among the clans those who reject a part thereof. Say: "I am commanded to worship Allah, and not to join partners with Him. Unto Him do I call, and unto Him is my return''.
Quran states
وَمَا أَنزَلْنَا عَلَيْكَ الْكِتَابَ إِلَّا لِتُبَيِّنَ لَهُمُ الَّذِي اخْتَلَفُوا فِيهِ ۙ وَهُدًى وَرَحْمَةً لِّقَوْمٍ يُؤْمِنُونَ
And We sent down the Book to thee for the express purpose, that thou shouldst make clear to them those things in which they differ, and that it should be a guide and a mercy to those who believe.
يَعْمَلُونَ لَهُ مَا يَشَاءُ مِن مَّحَارِيبَ وَتَمَاثِيلَ وَجِفَانٍ كَالْجَوَابِ وَقُدُورٍ رَّاسِيَاتٍ ۚ اعْمَلُوا آلَ دَاوُودَ شُكْرًا ۚ وَقَلِيلٌ مِّنْ عِبَادِيَ الشَّكُور
They worked for him as he desired, (making) arches, images, basons as large as reservoirs, and (cooking) cauldrons fixed (in their places): "Work ye, sons of David, with thanks! but few of My servants are grateful.
All realities will appear in the doomsday and whatever is denied should be revealed as Quran states
إِنَّهُ عَلَىٰ رَجْعِهِ لَقَادِرٌ
.(Surely (Allah) is able to bring him back (to life
يَوْمَ تُبْلَى السَّرَائِرُ
The Day that (all) things secret will be tested.
وَأَخْرَجَتِ الْأَرْضُ أَثْقَالَهَا
And the earth throws up her burdens (from within).
Quran states about secrets in the world
وَإِن تَجْهَرْ بِالْقَوْلِ فَإِنَّهُ يَعْلَمُ السِّرَّ وَأَخْفَى
If thou pronounce the word aloud, (it is no matter): for verily He knoweth what is secret and what is yet more hidden.
Quran states
يَوْمَئِذٍ يَوَدُّ الَّذِينَ كَفَرُوا وَعَصَوُا الرَّسُولَ لَوْ تُسَوَّىٰ بِهِمُ الْأَرْضُ وَلَا يَكْتُمُونَ اللَّهَ حَدِيثًا
On that day those who reject Faith and disobey the messenger will wish that the earth Were made one with them: But never will they hide a single fact from Allah.
Prophets say
يَا أَهْلَ الْكِتَابِ لِمَ تَلْبِسُونَ الْحَقَّ بِالْبَاطِلِ وَتَكْتُمُونَ الْحَقَّ وَأَنتُمْ تَعْلَمُونَ
Ye People of the Book! Why do ye clothe Truth with falsehood, and conceal the Truth, while ye have knowledge.
All of body organs and things will express reality;
وَقَالُوا لِجُلُودِهِمْ لِمَ شَهِدتُّمْ عَلَيْنَا ۖ قَالُوا أَنطَقَنَا اللَّهُ الَّذِي أَنطَقَ كُلَّ شَيْءٍ وَهُوَ خَلَقَكُمْ أَوَّلَ مَرَّةٍ وَإِلَيْهِ تُرْجَعُون
They will say to their skins: "Why bear ye witness against us?" They will say: "Allah hath given us speech,- (He) Who giveth speech to everything: He created you for the first time, and unto Him were ye to return.
فَذَٰلِكُمُ اللَّهُ رَبُّكُمُ الْحَقُّ ۖ فَمَاذَا بَعْدَ الْحَقِّ إِلَّا الضَّلَالُ ۖ فَأَنَّىٰ تُصْرَفُونَ
Such is Allah, your real Cherisher and Sustainer: apart from truth, what (remains) but error? How then are ye turned away?
بَلْ نَقْذِفُ بِالْحَقِّ عَلَى الْبَاطِلِ فَيَدْمَغُهُ فَإِذَا هُوَ زَاهِقٌ ۚ وَلَكُمُ الْوَيْلُ مِمَّا تَصِفُونَ
Nay, We hurl the Truth against falsehood, and it knocks out its brain, and behold, falsehood doth perish! Ah! woe be to you for the (false) things ye ascribe (to Us).
Quran states about the doomsday
وَلِلَّهِ غَيْبُ السَّمَاوَاتِ وَالْأَرْضِ ۚ وَمَا أَمْرُ السَّاعَةِ إِلَّا كَلَمْحِ الْبَصَرِ أَوْ هُوَ أَقْرَبُ ۚ إِنَّ اللَّهَ عَلَىٰ كُلِّ شَيْءٍ قَدِيرٌ
To Allah belongeth the Mystery of the heavens and the earth. And the Decision of the Hour (of Judgment) is as the twingkling of an eye, or even quicker: for Allah hath power over all things.
The world is potential stage of the afterlife as Quran states
وَمَا هَٰذِهِ الْحَيَاةُ الدُّنْيَا إِلَّا لَهْوٌ وَلَعِبٌ ۚ وَإِنَّ الدَّارَ الْآخِرَةَ لَهِيَ الْحَيَوَانُ ۚ لَوْ كَانُوا يَعْلَمُونَ
What is the life of this world but amusement and play? but verily the Home in the Hereafter,- that is life indeed, if they but knew.
وَلَهُ مَن فِي السَّمَاوَاتِ وَالْأَرْضِ ۚ وَمَنْ عِندَهُ لَا يَسْتَكْبِرُونَ عَنْ عِبَادَتِهِ وَلَا يَسْتَحْسِرُونَ
To Him belong all (creatures) in the heavens and on earth: Even those who are in His (very) Presence are not too proud to serve Him, nor are they (ever) weary (of His service).
Quran states about revealing of secrets
وَيَسْأَلُونَكَ عَنِ الْجِبَالِ فَقُلْ يَنسِفُهَا رَبِّي نَسْفًا
They ask thee concerning the Mountains: say, "My Lord will uproot them and scatter them as dust''.
فَيَذَرُهَا قَاعًا صَفْصَفًا
He will leave them as plains smooth and level.
لَّا تَرَىٰ فِيهَا عِوَجًا وَلَا أَمْتًا
Nothing crooked or curved wilt thou see in their place.
Quran states that we should follow persons that God has considered them sincere persons;
إِنَّا أَخْلَصْنَاهُم بِخَالِصَةٍ ذِكْرَى الدَّارِ
Verily We did choose them for a special (purpose)- proclaiming the Message of the Hereafter.
As a matter of fact, remembering God is considered as the best blessing from God as Quran states
وَذَرِ الَّذِينَ اتَّخَذُوا دِينَهُمْ لَعِبًا وَلَهْوًا وَغَرَّتْهُمُ الْحَيَاةُ الدُّنْيَا ۚ وَذَكِّرْ بِهِ أَن تُبْسَلَ نَفْسٌ بِمَا كَسَبَتْ لَيْسَ لَهَا مِن دُونِ اللَّهِ وَلِيٌّ وَلَا شَفِيعٌ وَإِن تَعْدِلْ كُلَّ عَدْلٍ لَّا يُؤْخَذْ مِنْهَا ۗ أُولَٰئِكَ الَّذِينَ أُبْسِلُوا بِمَا كَسَبُوا ۖ لَهُمْ شَرَابٌ مِّنْ حَمِيمٍ وَعَذَابٌ أَلِيمٌ بِمَا كَانُوا يَكْفُرُونَ
Leave alone those who take their religion to be mere play and amusement, and are deceived by the life of this world. But proclaim (to them) this (truth): that every soul delivers itself to ruin by its own acts: it will find for itself no protector or intercessor except Allah: if it offered every ransom, (or reparation), none will be accepted: such is (the end of) those who deliver themselves to ruin by their own acts: they will have for drink (only) boiling water, and for punishment, one most grievous: for they persisted in rejecting Allah.
وَمَا قَدَرُوا اللَّهَ حَقَّ قَدْرِهِ إِذْ قَالُوا مَا أَنزَلَ اللَّهُ عَلَىٰ بَشَرٍ مِّن شَيْءٍ ۗ قُلْ مَنْ أَنزَلَ الْكِتَابَ الَّذِي جَاءَ بِهِ مُوسَىٰ نُورًا وَهُدًى لِّلنَّاسِ ۖ تَجْعَلُونَهُ قَرَاطِيسَ تُبْدُونَهَا وَتُخْفُونَ كَثِيرًا ۖ وَعُلِّمْتُم مَّا لَمْ تَعْلَمُوا أَنتُمْ وَلَا آبَاؤُكُمْ ۖ قُلِ اللَّهُ ۖ ثُمَّ ذَرْهُمْ فِي خَوْضِهِمْ يَلْعَبُونَ
No just estimate of Allah do they make when they say: "Nothing doth Allah send down to man (by way of revelation)" Say: "Who then sent down the Book which Moses brought?- a light and guidance to man: But ye make it into (separate) sheets for show, while ye conceal much (of its contents): therein were ye taught that which ye knew not- neither ye nor your fathers." Say: "Allah (sent it down)": Then leave them to plunge in vain discourse and trifling''.
وَمَنْ أَظْلَمُ مِمَّنِ افْتَرَىٰ عَلَى اللَّهِ كَذِبًا أَوْ قَالَ أُوحِيَ إِلَيَّ وَلَمْ يُوحَ إِلَيْهِ شَيْءٌ وَمَن قَالَ سَأُنزِلُ مِثْلَ مَا أَنزَلَ اللَّهُ ۗ وَلَوْ تَرَىٰ إِذِ الظَّالِمُونَ فِي غَمَرَاتِ الْمَوْتِ وَالْمَلَائِكَةُ بَاسِطُو أَيْدِيهِمْ أَخْرِجُوا أَنفُسَكُمُ ۖ الْيَوْمَ تُجْزَوْنَ عَذَابَ الْهُونِ بِمَا كُنتُمْ تَقُولُونَ عَلَى اللَّهِ غَيْرَ الْحَقِّ وَكُنتُمْ عَنْ آيَاتِهِ تَسْتَكْبِرُونَ
Who can be more wicked than one who inventeth a lie against Allah, or saith, "I have received inspiration," when he hath received none, or (again) who saith, "I can reveal the like of what Allah hath revealed"? If thou couldst but see how the wicked (do fare) in the flood of confusion at death! - the angels stretch forth their hands, (saying),"Yield up your souls: this day shall ye receive your reward,- a penalty of shame, for that ye used to tell lies against Allah, and scornfully to reject of His signs''.
وَمَا لَكُمْ أَلَّا تَأْكُلُوا مِمَّا ذُكِرَ اسْمُ اللَّهِ عَلَيْهِ وَقَدْ فَصَّلَ لَكُم مَّا حَرَّمَ عَلَيْكُمْ إِلَّا مَا اضْطُرِرْتُمْ إِلَيْهِ ۗ وَإِنَّ كَثِيرًا لَّيُضِلُّونَ بِأَهْوَائِهِم بِغَيْرِ عِلْمٍ ۗ إِنَّ رَبَّكَ هُوَ أَعْلَمُ بِالْمُعْتَدِينَ
Why should ye not eat of (meats) on which Allah´s name hath been pronounced, when He hath explained to you in detail what is forbidden to you - except under compulsion of necessity? But many do mislead (men) by their appetites unchecked by knowledge. Thy Lord knoweth best those who transgress''.