Surah Al-Nahl (The Bees), Verse 93

وَلَوْ شَآءَ اللّٰهُ لَجَعَلَكُمْ اُمَّةً وَّاحِدَةً وَّلٰكِنْ یُّضِلُّ مَنْ یَّشَآءُ وَیَهْدِیْ مَنْ یَّشَآءُ وَلَتُسْـَٔلُنَّ عَمَّا كُنْتُمْ تَعْمَلُوْنَ ۟

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

“If Allah so willed, He could make you all one people: But He leaves straying whom He pleases, and He guides whom He pleases: but ye shall certainly be called to account for all your actions.”

Quran 16:93 (Yusuf Ali Translation)