وَلَوْ شَاۤءَ اللّٰهُ لَجَعَلَكُمْ اُمَّةً وَّاحِدَةً وَّلٰكِنْ يُّضِلُّ مَنْ يَّشَاۤءُ وَيَهْدِيْ مَنْ يَّشَاۤءُۗ وَلَتُسْـَٔلُنَّ عَمَّا كُنْتُمْ تَعْمَلُوْنَ ( النحل: ٩٣ )
Wa law shaaa'al laahu laja'alakum ummmatanw waahidatanw wa laakiny yudillu many-yashaaa'u wa yahdee many-yashaaa'; wa latus'alunna 'ammaa kuntum ta'maloon (an-Naḥl 16:93)
And if Allah had willed, He could have made you [of] one religion, but He sends astray whom He wills and guides whom He wills. And you will surely be questioned about what you used to do. (An-Nahl  : 93)
1 Mufti Taqi Usmani
If Allah so willed, He would have made all of you a single community, but He lets whom He wills go astray and takes whom He wills to the right path; and surely you will be questioned about what you used to do.