﴿ وَمَا كَانَ ٱلنَّاسُ إِلَّآ أُمَّةًۭ وَٰحِدَةًۭ فَٱخْتَلَفُوا۟ ۚ وَلَوْلَا كَلِمَةٌۭ سَبَقَتْ مِن رَّبِّكَ لَقُضِىَ بَيْنَهُمْ فِيمَا فِيهِ يَخْتَلِفُونَ ﴾

“AND [know that] all mankind were once but one single community, and only later did they begin to hold divergent views. And had it not been for a decree- that had already gone forth from thy Sustainer, all their differences would indeed have been settled [from the outset].”

God initially grounded human existence in the religion of nature. At that time, the religion of all humanity was one and the same. But, people had their differences and devised different forms of religions. The reason for this is the misuse of the freedom given to the people for the purpose of testing them. If God were to reveal Himself, human arrogance would come to an end on observing His powers, and suddenly unity would replace differences, because extremity of fear demolishes a multiplicity of opinions. But God will not intervene in this state of affairs before Judgement Day. God had created the present world for the sake of putting human beings to the test, and to maintain the atmosphere of testing, it is necessary to keep the reality concealed, so that people should have the opportunity to use their wisdom in both right and wrong directions.