The Qur'an alludes to the inevitability of dissension among human beings: in other words, it is the will of God that their way to the truth should be marked by conflicts and trial by error, here some references from Quran:
2:213. Mankind was one single nation, and Allah sent Messengers with glad tidings and warnings; and with them He sent the Book In truth, to judge between people in matters wherein they differed; but the people of the Book, after the Clear Signs came to them, did not differ among themselves, except through selfish contumacy. Allah by His Grace guided the believers to the truth, concerning that wherein they differed for Allah guides to straight way him who [wills to be guided].
Let there be no compulsion In religion: truth stands out Clear from error: Whoever rejects evil and believes In Allah hath grasped the Most trustworthy hand-hold, that never breaks. and Allah heareth and knoweth all things.
وَأَنزَلْنَا إِلَيْكَ الْكِتَابَ بِالْحَقِّ مُصَدِّقًا لِّمَا بَيْنَ يَدَيْهِ مِنَ الْكِتَابِ وَمُهَيْمِنًا عَلَيْهِ ۖ فَاحْكُم بَيْنَهُم بِمَا أَنزَلَ اللَّـهُ ۖ وَلَا تَتَّبِعْ أَهْوَاءَهُمْ عَمَّا جَاءَكَ مِنَ الْحَقِّ ۚ لِكُلٍّ جَعَلْنَا مِنكُمْ شِرْعَةً وَمِنْهَاجًا ۚ وَلَوْ شَاءَ اللَّـهُ لَجَعَلَكُمْ أُمَّةً وَاحِدَةً وَلَـٰكِن لِّيَبْلُوَكُمْ فِي مَا آتَاكُمْ ۖ فَاسْتَبِقُوا الْخَيْرَاتِ ۚ إِلَى اللَّـهِ مَرْجِعُكُمْ جَمِيعًا فَيُنَبِّئُكُم بِمَا كُنتُمْ فِيهِ تَخْتَلِفُونَ
Then We revealed the Book to you (O Muhammad!) with Truth, confirming whatever of the Book was revealed before, and protecting and guarding over it. Judge, then, in the affairs of men in accordance with the Law that Allah has revealed, and do not follow their desires in disregard of the Truth which has come to you. For each of you We have appointed a Law and a way of life.
If Allah wanted He could have made all of you a single nation. But He willed otherwise in order to test you in what He has given you; therefore try to excel one another in good deeds. Ultimately you all shall return to Allah; then He will show you the truth of those matters in which you dispute.
Why do the religious laws propounded by the various Prophets differ in matters of detail even though the Prophets and their Books preach one and the same religion (din) and even confirm and support each other? Why is it that in regard to the prescribed forms of worship, the regulations concerning what is permitted and what is prohibited, and the detailed legal regulations governing the social and collective life, there is some disagreement among the various laws propounded by the different Prophets and the divine Books?
This constitutes a detailed answer to the above question. It consists of the following points:
(1) It is a mistake to think that variations in religious laws result from a difference of source. It is God Himself Who altered the legal prescriptions to suit different nations at different times and in different circumstances.
(2) It was indeed possible, by divising one legal code for all human beings, for all men to have been made into one nation (ummah). But one of the many benevolent considerations keeping the religious laws of various Prophets different from one another was that God wanted this difference to become a means of testing people. Those who understand true religion, who have grasped its spirit and essence, and who are aware of the true importance of the different legal prescriptions, always recognize the Truth and accept it whatever its form. They have no hesitation in accepting the new ordinances of God in place of the old ones, in contrast to those who are not conversant with the spirit of true religion and who seem to identify it with a specific body of legal minutiae. Such people have overlaid God-given principles with their own legal deductions, and have sub sequently fossilized this entire amalgam, seeking to preserve it in its entirety. They have grown so attached to it that, in order to preserve it, they spurn every directive which subsequently comes to them from God. In order to distinguish the people of the first category from those of the second God made the legal prescriptions of the various Prophets vary.
(3) The real purpose of all the divine religious laws is the attainment of goodness and righteousness. This purpose can be achieved only when a man obeys whatever commandment he receives from God at a particular time. The proper mode of conduct for people who keep their eyes fixed on this true purpose is to strive for God's good pleasure rather than quarrel about differences in the legal prescriptions of the various Prophets.
(4) The differences which have arisen because of the unjustified rigidity, prejudice, obduracy and erroneous attitudes of the human mind can be finally settled neither in the debating hall nor on the battlefield. The final judgement will be made by God Himself. Then the reality of everything will be fully uncovered, and it will be clear how much truth and falsehood underlay the squabbles which whole lives were wasted over.
O mankind! Have fear of your Lord, the One who created you from a single soul, from that soul He created its mate, and through them He spread countless men and women. Fear Allah, the One in whose name you demand your rights from one another and the ties of relationship; surely Allah is watching you very closely.
It is He who created you from a single person and made his mate of like nature in order that he might dwell with her (in love). When they are united she bears a light burden and carries it about (unnoticed). When she grows heavy they both pray to Allah their Lord (saying): "if Thou give us a goodly child we vow we shall (ever) be grateful."
That was the reasoning about Us which We gave to Abraham (to use) against his people: We raise whom We will degree after degree: for thy Lord is full of wisdom and knowledge. We gave him Isaac and Jacob: all (three) We guided: and before him We guided Noah and before him We guided Noah and among his progeny David Solomon Job Joseph Moses and Aaron: thus do We reward those who do good: And Zachariah and John and Jesus and Elias: all in the ranks of the righteous: And Ishmael and Elisha and Jonah and Lot: and to all We gave favour above the nations: (To them) and to their fathers and progeny and brethren: We chose them. And We guided them to a straight way. This is the guidance of Allah: He gives that guidance to whom He pleases of His worshippers. If they were to join other gods with Him all that they did would be vain for them. These were the men to whom We gave the Book and authority and prophethood: if these (their descendants) reject them behold! We shall entrust their charge to a new People who reject them not. Those were the (prophets) who received Allah's guidance: copy the guidance they received; Say: "No reward for this do I ask of you: this is no less than a Message for the nations."
Some of these apostles have We endowed more highly than others: among them were such as were spoken to by God [Himself], and some He has raised yet higher. And We vouchsafed unto Jesus, the son of Mary, all evidence of the truth, and strengthened him with holy inspiration. And if God had so willed, they who succeeded those [apostles] would not have contended with one another after all evidence of the truth had come to them; but [as it was,] they did take to divergent views, and some of them attained to faith, while some of them came to deny the truth. Yet if God had so willed, they would not have contended with one another: but God does whatever He wills.
Yet people have divided themselves into factions and each faction rejoices in its own doctrines
Those people have not valued the attributes of Allah, the way His attributes should be valued, who say: "Allah has never revealed anything to a human being." Ask them: "Who then sent down the Book (Torah) which Moses brought, a light and guidance for mankind? You have transcribed it on separate sheets, publishing some and suppressing much of that given knowledge, which neither you nor your forefathers previously possessed." If they do not answer, then just say: "Allah" and leave them alone with the discourse of their useless arguments.
Allah is the Protector of those who have faith: from the depths of darkness He will lead them forth into light. of those who reject Faith the patrons are the evil ones: from light They will lead them forth into the depths of darkness. They will be companions of the fire, to dwell therein (for ever).
It is not righteousness that ye turn your faces towards east or West [in prayer rituals]; but it is righteousness- to believe In Allah and the Last Day, and the angels, and the Book, and the Messengers; to spend of your substance, out of love for him, for your kin, for orphans, for the needy, for the wayfarer, for those who ask, and for the ransom of slaves; to be steadfast In prayer, and practice regular charity; to fulfil the contracts which ye have made; and to be firm and patient, In pain (or suffering) and adversity, and throughout all periods of panic such are the people of truth, the Allah fearing.
The Messenger believeth in what hath been revealed to Him from His Lord, As do the men of Faith. Each one (of them) believeth In Allah, His angels, His books, and His apostles. "We make no distinction (They say) between one and another of His apostles." and They say: "We hear, and we obey: (We seek) Thy forgiveness, Our Lord, and to Thee is the end of all journeys."
Say ye: "We believe In Allah, and the Revelation given to us, and to Abraham, Isma'il, Isaac, Jacob, and the Tribes, and that given to Moses and Jesus, and that given to (all) prophets from their Lord: we make no difference between one and another of them: and we bow to Allah (in Islam)."
Say: will ye dispute with us about Allah, seeing that He is Our Lord and your Lord; that we are responsible for Our doings and ye for yours; and that we are sincere (in Our Faith) In Him?
That was a people that hath passed away. They shall reap the fruit of what They did, and ye of what ye do! of their merits there is no question In your case!
……. but He causes not to stray, except those who forsake (the path)
It is not required of Thee (o Messenger., to set them on the right path, but Allah sets on the right path whom He pleases whatever of good ye give benefits your own souls, and ye shall only do so seeking the "Face" of Allah. whatever good ye give, shall be rendered back to you, and ye shall not be dealt with unjustly.
On no soul doth Allah place a burden greater than it can bear it gets every good that it earns, and it suffers every ill that it earns.
Those who reject Faith, and die rejecting,- on them is Allah’s curse, and the curse of angels, and of all mankind;
Say: "O Allah. Lord of power (and Rule), Thou gives power to whom Thou pleases, and Thou stripes off power from whom Thou pleases: Thou endues with honour whom Thou pleases, and Thou brings low whom Thou pleases In Thy hand is all good. Verily, over all things Thou hast power.
Allah forgives not (the sin of) joining other gods with Him but He forgives whom He pleases other sins than this: one who joins other gods with Allah hath strayed far away (from the right). [Note: Blasphemy in the spiritual kingdom is like treason in the political kingdom.]
"Shall I take for my protector any other than Allah the Maker of the heavens and the earth? And He is that feeds but is not fed." Say: "Nay! but I am commanded to be the first of those who surrenders un to him (in Islam) and be not thou of the company of those who join gods with Allah."
The Apostles are not sent to cancel man's limited free-will. They are sent to preach and teach, - to preach hope to the repentant ("good news"), and to warn the rebellious of the Wrath to come:
We send the Apostles only to give good news and to warn: so those who believe and mend (their lives) upon them shall be no fear nor shall they grieve. But those who reject Our Signs them shall our punishment touch for that they ceased not from transgressing. Say: "I tell you not that with me are the treasures of Allah nor do I know what is hidden nor do I tell you I am an angel. I but follow what is revealed to me." Say: "Can the blind be held equal to the seeing?" Will ye then consider not?
To Him is due the primal origin of the heavens and the earth: how can He have a son when He hath no consort? He created all things and He hath full knowledge of all things. That is Allah your Lord! there is no god but He the Creator of all things: then worship ye Him: and He hath power to dispose of all affairs. No vision can grasp Him but His grasp is over all vision: He is above all comprehension yet is acquainted with all things. "Now have come to you from your Lord proofs to open your eyes: if any will see it will be for (the good of) his own soul; if any will be blind it will be to his own (harm): I am not (here) to watch over your doings." Thus do We explain the Signs by various (symbols): that they may say "Thou hast taught us diligently" and that We may make the matter clear to those who know. Follow what thou art taught by inspiration from thy Lord: there is no god but He: and turn aside from those who join gods with Allah.