Al-Muddaththir • EN-AL-JALALAYN
﴿ كَلَّا ۖ بَل لَّا يَخَافُونَ ٱلْءَاخِرَةَ ﴾
“Nay, but they do not [believe in and, hence, do not] fear the life to come.”
No indeed! kallā a deterrent of what they desire. Rather they do not fear the Hereafter that is the chastisement thereof.