Even if an enemy of yours meets their death, so what? And if he remains alive, then what? To cause benefit or harm lies within the power and control of the Almighty God. No human being can cause harm to another.
Sa‘di has written an anecdote in his Gulistan that someone brought the good news to Nusherwan that a certain enemy of his had been killed, and that his country and fortress had been taken over by Nusherwan’s forces.
Nusherwan gave a marvellous response:
The death of my enemy brings me no joy; For even our own life is not forever.
(Malfuzat, Vol. 1, p. 359)