Hud - 11:118

وَلَوْ شَاء رَبُّكَ لَجَعَلَ النَّاسَ أُمَّةً وَاحِدَةً وَلاَ يَزَالُونَ مُخْتَلِفِينَ
[11:118]
And if your Lord had pleased He would certainly have made people a single nation, and they shall continue to differ.
If thy Lord had so willed, He could have made mankind one people: but they will not cease to dispute.
And if thy Lord had willed, He verily would have made mankind one nation, yet they cease not differing,