Caution: Translations of Quran and Ḥadīth may lead to possible misapplications and misinterpretations. This site is intended for students of sacred knowledge that are proficient in comprehending classical Arabic and have a strong foundation in Islamic sciences. Also note that religious injunctions rely on several aspects beyond what one may glean through reading individual aḥādīth.
Qurʾān Bukhārī Muslim Nasāʾī Abū Dāwūd Tirmidhī Ibn Mājah Mālik Aḥmad Dārimī Ḥākim Ibn Ḥibbān Ṭabarānī Nasāʾī's Kubrá Bayhaqī al-Luʾluʾ wa-al-Marjān Ibn Rajab's Fifty Riyāḍ al-Ṣāliḥīn Aḥmad's Zuhd Suyūṭī
quran:11:118 –

And if your Lord had willed, He could have made mankind one community; but they will not cease to differ.  

Had your Lord willed, He would have made mankind one community, people of one religion, but they continue to differ, in religion,
القرآن:١١:١١٨ –

وَلَوْ شَاءَ رَبُّكَ لَجَعَلَ النَّاسَ أُمَّةً وَاحِدَةً ۖ وَلَا يَزَالُونَ مُخْتَلِفِينَ  

{ولو شاء ربك لجعل الناس أمَّة واحدة} أهل دين واحد {ولا يزالون مختلفين} في الدين.