From Book 21 of Imaam Al-Ghazzali’s Ihya Ulum Al-din
v Know, that the heart is like a fortress. Shaytaan is an enemy who wishes to enter the fortress and take possession of it.
v The fortress cannot be kept safe from the enemy except by guarding its doors and entrances.
v The doors in which shaytaan enters, are the traits of a person
v He whom does not know his doors cannot guard them.
There are great doors and then there are narrow doors. These great doors are like the large street gates. Once you close the large street gates, it will become easier to close the narrow ones.
One of the great gates is Anger
- When one gets angry, this anger can overtake a person, the same way one gets intoxicated by alcohol; they lose control.
One must always be conscious of keeping the gates closed. If the army of the intellect grow weak (you are not conscious of it), then the army of shaytaan will take the opportunity to attack. When one becomes angry, shaytaan will play with that person as a boy plays with a ball (tossing it and kicking it here and there and making it do what he wants).
Of the great doors, includes: Anger, Desire, Greed, Hastiness – man is hasty by nature (Hastiness of anger is a characteristic of Man that is most helpful to shaytaan), love of adornment of furnishing and house, and the greatest door is Envy.
He whom does not know his doors cannot guard them.
So know them, and guard them.
