That is because they were hostile to Allah and His Messenger; and whoever becomes hostile to Allah and His Messenger, then, Allah is severe at punishment.

That is what you have to taste, and for the disbelievers is the (further) punishment of the Fire.

O you who believe, when you face the disbelievers in a battle, do not turn your backs to them.

Whoever turns his back to them on such a day,- unless it is for a tactic in the battle, or to join a company,-turns with wrath from Allah, and his abode is Jahannam (Hell), and it is an evil place to return.