[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
The Saheeh International Quran Translation
قَيِّمًا لِّيُنذِرَ بَأْسًا شَدِيدًا مِّن لَّدُنْهُ وَيُبَشِّرَ ٱلْمُؤْمِنِينَ ٱلَّذِينَ يَعْمَلُونَ ٱلصَّٰلِحَٰتِ أَنَّ لَهُمْ أَجْرًا حَسَنًا[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