Hour, All of a sudden it is on them

Those will have lost who deny the meeting with Allāh, until when the Hour [of resurrection] comes upon them unexpectedly, they will say, "Oh, [how great is] our regret over what we neglected concerning it [i.e., the Hour]," while they bear their burdens [i.e., sins] on their backs. Unquestionably, evil is that which they bear.

They ask you, [O Muḥammad], about the Hour: when is its arrival?¹ Say, "Its knowledge is only with my Lord. None will reveal its time except Him. It lays heavily² upon the heavens and the earth. It will not come upon you except unexpectedly." They ask you as if you are familiar with it. Say, "Its knowledge is only with Allāh, but most of the people do not know."

Then do they feel secure that there will not come to them an overwhelming [aspect] of the punishment of Allāh or that the Hour will not come upon them suddenly while they do not perceive?

Are they waiting except for the Hour to come upon them suddenly while they perceive not?