8:39

O believers, fight them until there is no more mischief (fitnah) and the Deen (religion) of Allah (way of life prescribed by Allah) is established completely; but if they do stop from mischief, then surely Allah is observant of all their actions.
Meaning:-
Fitnah: ( Al-Fitnah is worse than killing.) Spreading Mischief, trying to force the Muslims to revert from their religion and re-embrace Kufr after they had believed, is worse with Allah than killing.
observant: quick to notice things. looking at, watching.