Quran 11:118 from Surah Hud on Divine Marvels.
وَلَوۡ شَآءَ رَبُّكَ لَجَعَلَ ٱلنَّاسَ أُمَّةٗ وَٰحِدَةٗۖ وَلَا يَزَالُونَ مُخۡتَلِفِينَ
English translation: And if your Lord (had) willed your Lord (had) willed surely He (could) have made the mankind one community one community but not they will cease to differ
Transliteration: walaw shaa rabbuka laja'ala al-nasa ummatan wahidatan wala yazaluna mukh'talifina