General Behavior (Kitab Al-Adab)
Dawud :: Book 41 : Hadith 5076
Narrated Anas ibn Malik:
The Prophet (peace_be_upon_him) said: When a man goes out of his house and says: "In the name of Allah, I trust in Allah; there is no might and no power but in Allah," the following will be said to him at that time: "You are guided, defended and protected." The devils will go far from him and another devil will say: How can you deal with a man who has been guided, defended and protected?