Ephesians 4:27:

Neither give place [opportunity] to the devil.

Notes on Ephesians 4:27:

The fact that you are commanded not to give the devil an opportunity proves that you have the power to shut him out.  It is not a matter of asking God to do something about the devil.  He did something about the devil when Christ defeated him.  He gave YOU authority over the devil, so it is up to you to use it.  If you don’t use your authority, nothing will improve, because God will not do anything about the devil for you.  It’s your job to resist the devil, not God’s job to resist him for you.

See also:

Casting Out the Spirit of Stupidity
How to Deal with the Devil
Who Is in Control of Your Life?
Hop on It!
Am I Sick Because I Left a Door Open to the Devil?
Is There a Danger That a Demon That Has Just Been Cast Out Will Go into Another Person Who Is Present?