﴿ قُلْ أَىُّ شَىْءٍ أَكْبَرُ شَهَٰدَةًۭ ۖ قُلِ ٱللَّهُ ۖ شَهِيدٌۢ بَيْنِى وَبَيْنَكُمْ ۚ وَأُوحِىَ إِلَىَّ هَٰذَا ٱلْقُرْءَانُ لِأُنذِرَكُم بِهِۦ وَمَنۢ بَلَغَ ۚ أَئِنَّكُمْ لَتَشْهَدُونَ أَنَّ مَعَ ٱللَّهِ ءَالِهَةً أُخْرَىٰ ۚ قُل لَّآ أَشْهَدُ ۚ قُلْ إِنَّمَا هُوَ إِلَٰهٌۭ وَٰحِدٌۭ وَإِنَّنِى بَرِىٓءٌۭ مِّمَّا تُشْرِكُونَ ﴾

“Say: "What could most weightily bear witness to the truth?" Say: "God is witness between me and you; and this Qur’an has been revealed unto me so that on the strength thereof I might warn you and all whom it may reach." Could you in truth bear witness that there are other deities side by side with God? Say: "I bear no [such] witness!" Say: "He is the One God; and, behold, far be it from me to ascribe divinity, as, you do, to aught beside Him!"”

In the on-going struggle between the proponents, on the one hand of Truth and on the other of falsehood, the only decisive factor is the Book of God. There is nobody who knows the full facts or has any real authority except God. So God, the only Being who is capable of settling this dispute, has given an arbiter to the people in the form of the Quran. Now, man has only one course open to him. If he is not aware of the veracity of the Quran, he should investigate and satisfy himself that it is the Book of God. When he comes to know that it is really the Book of God, he should necessarily be satisfied with whatever is advocated therein. One who is not in agreement with the decision of the Quran runs the risk of being forced to accept its verdict in the Hereafter after much degradation and punishment. The Quran has been revealed so that, before the arrival of the time of Judgement, people may be made aware of what awaits them. The Prophet Muhammad performed this task during his prophethood and the same work has to be continued by his followers (ummah) till Doomsday. The Quran tells us in advance how God is going to treat people in the eternal world of the Hereafter. Those who are assigned the task of delivering this message to the people will be free of the responsibility once they have fully conveyed the message; but those to whom it is delivered will be free in the eyes of God only when they have accepted it and reformed themselves accordingly. The missionary’s responsibility ends with his ‘preaching’, while that of the addressee ends only on his ‘fulfilling his religious obligations’.