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

“[a divine writ] unerringly straight, meant to warn [the godless] of a severe punishment from Him, and to give unto the believers who do good works the glad tiding that theirs shall be a goodly reward-”

((But hath made it) straight) and it is also said that this means: custodian over all other Scriptures, (to give warning) so that Muhammad (pbuh) gives warning by means of the Qur'an (of stern punishment from Him, and to bring) and so that Muhammad brings the Qur'an (unto the) sincere (believers who do good works) between them and their Lord (the news that theirs will be a fair reward) they will have a fair reward in Paradise.