In the Qur’an, God Almighty says that had it not been for a thing already decided, their matter would have been decided, i.e. they would have perished.
[42.14] And they did not become divided until after knowledge had come to them out of envy among themselves; and had not a word gone forth from your Lord till an appointed term, certainly judgment would have been given between them; and those who were made to inherit the Book after them are most surely in.
The verse above speaks of Jews and Christians dividing their religion after clear knowledge had come to them. It is stated that their matter would have been decided had it not been for a word already gone forth. From the explanations above, it appears that this word was the promise of the end times and destruction at the hands of the messenger they rejected i.e. Prophet Issa (peace be upon him). The verse does speak of an appointed time for this promise to happen and this delay in the punishment is given to these disbelievers until Prophet Issa (peace be upon him) returns.
[41.45] And certainly We gave the Book to Moosa, but it has been differed about, and had not a word already gone forth from your Lord, judgment would certainly have been given between them; and most surely they are in a disquieting doubt about it.