The adoption of four characteristics protect a person from Shayṭān and his entry into the Fire becomes forbidden: The one who is able to exert control over himself in the face of desire, terror, lust, and anger.”
[Ibn Rajab comments]: These four (characteristics) are the very foundations of evil in its entirety.
As for desire, it is for a soul to incline towards something under the supposition that thing offers the procurement of some benefit. Should a person desire something, this will drive him to seek out the object of his desire by any means necessary provided he believes his means are fruitful. Many of those means may be forbidden. Furthermore, it may also be that the object of his desire is itself forbidden.
As for terror, it is to harbour intense fear of something. When a person fears something, he begins to defend himself from it by any and all means he believes will prevent it from reaching him. It may be that many of these incorporated means are forbidden.
As for lust, it is for the soul to incline towards that which it perceives as satisfying, from which it can derive wanton enjoyment. It may incline, in many instances, towards that which is forbidden for it: fornication, stealing, and drinking intoxicants. Furthermore, it may even lead to outright disbelief: magic [through enlisting the help of the jinn by means of shirk], hypocrisy, and innovation.
As for anger, it is the boiling of the blood of one’s heart in opposition to perceived harm or seeking vengeance from an attacker following the occurrence of harm. This results in many forbidden acts including: murder, fighting, oppression of various kinds, enmity, forbidden variants of speech like slander, insults, and obscenities. It may even be exacerbated and raised to the level of outright disbelief as was the case for Jabalah ibn al-Ayham. [Finally], it may cause one to take oaths of which its fulfilment would be ḥarām or cause one to regretfully divorce his spouse.
Source: Jāmiʿ al-Ulūm 1:410
Translated by: Riyāḍ al-Kanadī