وَمَا كَانَ النَّاسُ اِلَّآ اُمَّةً وَّاحِدَةً فَاخْتَلَفُوْاۗ وَلَوْلَا كَلِمَةٌ سَبَقَتْ مِنْ رَّبِّكَ لَقُضِيَ بَيْنَهُمْ فِيْمَا فِيْهِ يَخْتَلِفُوْنَ ( يونس: ١٩ )
Wa maa kaanan naasu illaaa ummmatanw waahidatan fakh talafoo; wa law laa kalimatun sabaqat mir Rabbika laqudiya bainahum fee maa feehi yakhtalifoon (al-Yūnus 10:19)
And mankind was not but one community [united in religion], but [then] they differed. And if not for a word that preceded from your Lord, it would have been judged between them [immediately] concerning that over which they differ. (Yunus  : 19)
1 Mufti Taqi Usmani
All the people were no more than a single community; later, they differed. But for a word from your Lord that had already come to pass, a decisive judgment would have been made about their mutual differences.