Qur'an 18:2 · Al-Kahf

قَيِّمًۭا لِّيُنذِرَ بَأْسًۭا شَدِيدًۭا مِّن لَّدُنْهُ وَيُبَشِّرَ ٱلْمُؤْمِنِينَ ٱلَّذِينَ يَعْمَلُونَ ٱلصَّٰلِحَٰتِ أَنَّ لَهُمْ أَجْرًا حَسَنًۭا

(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 [i.e., Paradise]