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:16:22 –

Your god is one God. But those who do not believe in the Hereafter - their hearts are disapproving, and they are arrogant.  

Your God, the One deserving of your worship, is One God, without ˹any˺ equal in ˹terms of˺ His essence or His attributes, and this is God, exalted He be. But as for those who do not believe in the Hereafter their hearts are in denial, rejecting the Oneness ˹of God˺, and they are arrogant, scorning to believe in it.
القرآن:١٦:٢٢ –

إِلَٰهُكُمْ إِلَٰهٌ وَاحِدٌ ۚ فَالَّذِينَ لَا يُؤْمِنُونَ بِالْآخِرَةِ قُلُوبُهُمْ مُنْكِرَةٌ وَهُمْ مُسْتَكْبِرُونَ  

{إلهكم} المستحق للعبادة منكم {إله واحد} لا نظير له في ذاته ولا في صفاته وهو الله تعالى {فالذين لا يؤمنون بالآخرة قلوبهم منكرة} جاحدة للوحدانية {وهم مستكبرون} متكبرون عن الإيمان بها.