You are reading a tafsir for the group of verses 17:9 to 17:10
Praising the Qur'an
Allah praises His noble Book, the Qur'an, which He revealed to His Messenger Muhammad ﷺ. It directs people to the best and clearest of ways.
وَيُبَشِّرُ الْمُؤْمِنِينَ
(gives good news to those who believe,) in it a
الَّذِينَ يَعْمَلُونَ الصَّـلِحَاتِ
(those who do righteous deeds,) in accordance with it, telling them
أَنَّ لَهُمْ أَجْرًا كَبِيرًا
(that they will have a great reward,) i.e., on the Day of Resurrection. And He tells
وأَنَّ الَّذِينَ لاَ يُؤْمِنُونَ بِالاٌّخِرَةِ
(those who do not believe in the Hereafter,) that
لَهُمْ عَذَاباً أَلِيماً
(for them is a painful torment,) i.e. on the Day of Resurrection. As Allah says:
فَبَشِّرْهُمْ بِعَذَابٍ أَلِيمٍ
(... then announce to them a painful torment.) 84:24