Words on fearing Allah [al-Khawf]
All praise be to Allah and peace and blessings be upon the Messenger of Allah.
Fearing Allah is from among the loftiest ranks of worship and the most beneficial of all. It is obligatory for everyone to fear Allah.
Allah Almighty says in the Qur'an:
"So fear them not, but fear Me, if you are (true) believers" [Al-Imran: 175].
"But for him who [the true believer of Islâmic Monotheism] fears the standing before his Lord, there will be two Gardens (i.e. in Paradise) [Al-Rahman: 46].
Definition of Khawf:
•Expecting Allah's punishment in every breath.
•The strong belief in destiny.
•The heart's determination to avoid Allah's wrath upon feeling it.
•It is a distress that befalls oneself when expecting the occurrence of something bad.
Quotes on fearing Allah
•Abu Hafs 'Umar ibn Maslama al-Haddad al-Nisaburi said: "Fearing Allah is a light in one's heart through which he/she can distinguish between good and bad. When we fear anyone we run away from him; unlike Allah the Almighty to Whom we flee. Therefore, the one who truly fears his Lord, flee to Him". A
•Abu Solaiman said: "A heart that loses the fear of Allah will end up as a loser".
•Ibrahim ibn Sufyan said: "when the fear of Allah is instilled in the hearts, it burns the spots of lusts and leads the believer to refrain from worldly pleasures."
•Dhu An-Nun said: "The believers are on the straight path as long as they fear Allah; otherwise, they will go astray."
The sincere praised kind of fear is that which prevents the believer from approaching what Allah prohibited. If a believer blindly exaggerates his fear, he will end up in losing hope in Allah's mercy.
Abu 'Uthman al-Hiri said: "Sincere fear is to refrain from committing sins in one's outward and inward actions."
Sheikh al-Islam, ibn Taymiya said: "praised fear is that which prevents a believer from approaching what Allah prohibited".
Obligatory and recommended fear
Obligatory fear is that which exhorts the believer to observe the obligations and refrain from prohibitions.
Recommended fear is that which exhorts the believer to observe recommended acts and refrain from what is detested.
See the detailed hadith on fearing Allah in Madarig As-Salikeen 1/507-513 and the comment on the book of Tawheed, the chapter titled: "It is only Shaitân (Satan) that suggests to you the fear of his Auliyâ' [supporters and friends".