﴿ فَيَأْتِيَهُم بَغْتَةًۭ وَهُمْ لَا يَشْعُرُونَ ﴾

“that will come upon them [on resurrection,] all of a sudden, without their being aware [of its approach];”

So that it) the torment (will come upon them suddenly, when they perceive not) the coming of the punishment upon them.