لِكُلِّ ٱمْرِئٍ مِّنْهُمْ يَوْمَئِذٍ شَأْنٌ يُغْنِيهِ
Likul limri-im-minuhm yaumaa-izin shaa nuy-yughneeh
each of them will be absorbed in concerns of their own on that Day-
on that day, every person will have concern enough to occupy them.
The three lines before this move outward through the closest ties in order, brother, then parents, then wife and children, so that the hardest separation stands last. What this verse gives as the cause is preoccupation: each person carries an affair of their own that suffices, filling the whole of their attention. The verb chosen for it is the one for having enough, and the flight described needs nothing crueller than that.