Holy Quran » HUUD : 118

11 : 118

وَلَوْ شَاء رَبُّكَ لَجَعَلَ النَّاسَ أُمَّةً وَاحِدَةً وَلاَ يَزَالُونَ مُخْتَلِفِينَ

And if your Lord had willed, He could have made mankind one community; but they will not cease to differ.

Tafseer

{ ولو شاء ربك لجعل الناس أمَّة واحدة } أهل دين واحد { ولا يزالون مختلفين } في الدين .

Had your Lord willed to make people of one nation and the religion of the people one and still different in religion.