إِنَّ عَذَابَ رَبِّكَ لَوَاقِعٌ مَّا لَهُ مِن دَافِعٍ (the punishment of your Lord is sure to fall. There is nothing to push it back,....52:7-8) Verses 1-6 constituted swearing of an oath, and the present verse is jawab-ul-qasam or the fact for which the oath is sworn, assuring that the torment of Allah will come to pass, and none will be able to avert it.
The Incident of Sayyidna ` Umar ؓ
Sayyidna ` Umar ؓ one day recited Surah Tur. When he came to these verses, he heaved a cool sigh after which he fell ill for about twenty days. During his illness the people would visit him, not knowing what caused his illness. (Ibn Kathir)
Sayyidna Jubair Ibn Mut'im ؓ says that before embracing Islam, he once went to the holy city of Madinah to negotiate regarding the prisoners of the battle of Badr. When he arrived there, the Holy Prophet ﷺ was reciting Surah Tur in Maghrib salah and his voice could be heard outside the mosque. When he recited verses [ 7] and [ 81: 'The punishment of your Lord is sure to fall. There is nothing to push it back,' He suddenly felt that his heart would burst through fear. He instantly embraced Islam. He felt at the time that he would not be able to move unless the torment would descend on him. (Qurtubi)