وَإِذْ تَأَذَّنَ رَبُّكَ لَيَبْعَثَنَّ عَلَيْهِمْ إِلَىٰ يَوْمِ ٱلْقِيَٰمَةِ مَن يَسُومُهُمْ سُوٓءَ ٱلْعَذَابِ ۗ إِنَّ رَبَّكَ لَسَرِيعُ ٱلْعِقَابِ ۖ وَإِنَّهُۥ لَغَفُورٌۭ رَّحِيمٌۭ
How to read it
Wa 'idh' ta'adhdhana rabbuka layab'ʻathanna ʻalay'him' 'ilā yaw'mi l-qiyāmati man yassūmuhum' sū'a l-ʻadhābi . 'inna rabbaka lassarīʻu l-ʻiqābi . wa'innahu laghafūrun rraḥīmun
Behold! thy Lord did declare that He would send against them, to the Day of Judgment, those who would afflict them with grievous penalty. Thy Lord is quick in retribution, but He is also Oft-forgiving, Most Merciful.
Translation: Abdullah Yusuf Ali

