It is attained by remembering the torment that burns the soul and the Day of Reckoning. Allah has stated that His own walī (friend[s] of God) have attained these through His grace and generosity. (Ri'āya, 24)
He said: Tahwīf bi'l-fikr (frightening through contemplation) is to frighten the nafs (the lower self) by reflecting on the states of the Hereafter, the coming of death, the greatness of Allah, one's obligations, and the possibility of failing to fulfill these commands and avoid prohibitions. I asked: Fikr (contemplation) feels burdensome to my qalb (the heart). How does it not feel burdensome to the hearts of (other) people who are not concerned with Sufism? He replied: Fikr is burdensome to servants for three reasons. In some people, all three come together, making contemplation burdensome for them. In others, one or two of these reasons combine, so it is also burdensome for them. The first is that the qalb loses its comfort due to gazing at the dunya (this world). For when a person engages in tafakkur (contemplation), the mind turns away from the dunya, and by thinking about and being occupied with worldly matters, comfort is lost (when one thinks of the Hereafter, the world appears empty and meaningless).
The second reason is that when one remembers the states of the Hereafter, the reckoning, and the situations for and against oneself, contemplating the Hereafter and its severity brings pain and sorrow to the nafs. For when a resolute muwahhid (one who affirms tawhid) thinks about this, he is stirred by the grief and sorrow that arise from iman (faith). For this reason, contemplation is burdensome to the nafs, as the stirring grief and sorrows weigh heavily upon it.
The third point is that the nafs and the enemy (Satan) know that when the murīd (aspirant, disciple) contemplates the Hereafter, such contemplation is only sought to instill fear that will distance him from pleasures. Yet these pleasures do not bring him closer to his Lord, but rather cause him to resist what his Lord has obligated upon him and to commit undesirable acts. When the nafs realizes that throughout life it will be burdened with things it dislikes and that it will be required to abstain from itself and its pleasures, contemplation will certainly be burdensome to it. It also knows that it will be required to do things that thwart Satan's tricks, refute his arguments, and go against its own desires. Thus, for these three reasons, contemplation is burdensome for murīds. (Ri'āya, 25)
For whoever's sins increase and heedlessness persists, tahwīf (frightening) awakens him from his sleep and sobers him from his intoxication. (Ri'āya, 31)
When Shiblī was asked what khawf (fear of God) is, he replied: It is to fear that Allah will leave you to yourself.
Abū Saʿīd Harrāz says: I complained to one of the ʿārifūn (those who possess maʿrifa, experiential knowledge of God) about khawf. He said to me: I wish to see a man who knows what it means to fear Allah, and then added: Most of the people of khawf fear themselves, and they fear Allah in order to act and save themselves from His command. (Lumaʿ, 89)
Khawf and rajāʾ (hope) are the two wings of action; it is not possible to fly without them. Abū Bakr Warrāq says: Rajāʾ is a relief that comes to the qalb of the khāʾifūn (those who fear) from Allah, the Exalted. If there were no rajāʾ, their nafs would perish and their intellects would be lost.
Rajāʾ is of three kinds: hope in Allah, hope in the vastness of Allah's mercy, and hope in the abundance of reward that Allah will give. Hope in the vastness of Allah's mercy and the abundance of reward is as follows: The servant who is a murīd, having heard mention of Allah's favors, hopes that He will grant him these blessings. He knows that grace, generosity, and munificence are attributes of Allah, and his qalb finds peace with Allah, from whom grace and bounty are hoped. As narrated from Dhū'n-Nūn al-Miṣrī: In his supplication to Allah, he used to say: O Allah! Trusting in the vastness of Your mercy gives us more hope than relying on our own deeds. Trusting in Your forgiveness gives us more hope than fearing the punishment You may inflict.
Another person would supplicate: O my God! You are most gracious to the one who turns to You by his will and hopes in You amidst trials and calamities. O final destination of the desires of the people of rajāʾ! Grant us, even in this world, a joy that brings us to the stations of delight and to the maqām (spiritual station) of nearness!
The one who possesses rajāʾ in Allah is the one who has attained ḥaqīqa (inner reality) in rajāʾ and hopes for nothing except from Allah alone. As Shiblī replied when asked about rajāʾ: Rajāʾ is to hope that Allah does not place any barrier between you and Himself. (Lumaʿ, 91)
What are khawf and rajāʾ? They are the two reins of the nafs. Through them, the nafs does not deviate from its path and does not fall into idlāl (presenting one's deeds as proof of being a good servant to Allah), amn (feeling secure in one's own righteousness and final outcome), yaʾs (despair), or complete loss of hope, which lead to self-surrender.
Abū Bakr Wāsitī says: There are certain darknesses of khawf in which the one who is overtaken by khawf flounders under their dominance and seeks to escape from them at all costs. Then, when rajāʾ appears in all its brightness, the servant enters the field of peace and is overtaken by a state of longing. The beauty of the day is only beneficial through the darkness of the night. Both are necessary for the well-being of the world. The qalb is the same (like the world). Sometimes it is captive to the darkness of khawf. When the gleams of rajāʾ appear, it becomes radiant.
Maḥabba (love), khawf, and rajāʾ are closely related ḥāl (spiritual states). Thus, a Sufi says: Every maḥabba not accompanied by khawf is mere habit (an ordinary love). Every khawf not accompanied by rajāʾ is mere habit (an ordinary fear). Likewise, every rajāʾ not accompanied by khawf is the same. (Lumaʿ, 92)
Abū ʿAmr Dimashqī says: The khāʾif (one who fears Allah) is the one who fears his own nafs more than he fears the enemy (Satan).
Aḥmad Sayyid Ḥadrāwayh says: The khāʾif is the one whom the creatures fear.
Abū ʿAbdullah Jallā says: The khāʾif is the one whom the creatures feel safe with.
Ibn Hubayk says: The khāʾif is the one who acts according to the ruling of every moment; sometimes the creatures fear him, sometimes they trust him. The one whom the creatures fear is the one dominated by khawf. Thus, he becomes entirely khawf. Everything fears him. As it has been said: Everything fears the one who fears Allah. Even if the things that should cause fear dominate his mind, if he is absent from them due to fear of Allah, this does not affect him. Whoever is absent from things, things are also absent from him. (Taʿarruf, 68)
The first maqām of khawf is taqwa (God-consciousness). In this maqām are those who are muttaqī (God-conscious), righteous, and active in good deeds. The second maqām of khawf is ḥadhar (cautious avoidance). In this maqām are the ascetics, those with warāʿ (scrupulousness), and those with khushūʿ (humility). The third maqām is khashya. In this maqām are the scholars, the devout worshippers, and the muḥsinūn (those who practice ihsan, spiritual excellence). The fourth maqām is wajal. This is the maqām of those who engage in dhikr (remembrance of God), the humble, and the ʿārifūn. The fifth maqām is ishfāq (abstaining from evil out of reverence for the Lord). This is the maqām of the ṣiddīqūn (the truthful), the martyrs...