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:18:2 –

˹He has made it˺ straight, to warn of severe punishment from Him and to give good tidings to the believers who do righteous deeds that they will have a good reward  

˹a Book˺ upright, (qayyiman is a second circumstantial qualifier for ˹added˺ emphasis) to warn of, to make, by this Book, the disbelievers fear, severe chastisement from Him, from God, and to bring to the believers who perform righteous deeds the good tidings that theirs will be a fair reward,
القرآن:١٨:٢ –

قَيِّمًا لِيُنْذِرَ بَأْسًا شَدِيدًا مِنْ لَدُنْهُ وَيُبَشِّرَ الْمُؤْمِنِينَ الَّذِينَ يَعْمَلُونَ الصَّالِحَاتِ أَنَّ لَهُمْ أَجْرًا حَسَنًا  

{قيّما} مستقيما حال ثانية مؤكدة {لينذر} يخوف بالكتاب الكافرين {بأسا} عذابا {شديدا من لدنه} من قبل الله {ويبشر المؤمنين الذين يعملون الصالحات أن لهم أجرا حسنا}.