﴿ أَوْ يَأْخُذَهُمْ عَلَىٰ تَخَوُّفٍۢ فَإِنَّ رَبَّكُمْ لَرَءُوفٌۭ رَّحِيمٌ ﴾

“or take them to task through slow decay? And yet, behold, your Sustainer is most compassionate, a dispenser of grace!”

Or that He will not seize them amid growing fear? amid a gradual diminishing of their numbers little by little until all are destroyed ‘alā takhawwufin is a circumstantial qualifier referring to the subject of the verb God or the object. Indeed then your Lord is Gentle Merciful insofar as He does not hasten for them their punishment.