they ask you to hasten in bringing chastisement upon them. had there not been an appointed term for it the chastisement would have already visited them in fact it will come down upon them all of a sudden while they will not be aware of it.
ويستعجلونك بالعذاب ولولا أجل مسمى لجاءهم العذاب وليأتينهم بغتة وهم لا يشعرون