He gains mastery over his qalb (the heart): Allah will forgive him and bestow as much grace as He wills. He will become intimate with the feeling of hope (rajāʾ), allowing the world of his rūḥ (the spirit) to be influenced by hope, and the sense of shukr (gratitude) will grow in his heart. He will fear being punished for not showing gratitude to Him. During shukr, one should make it a habit to increase rajāʾ, so that Allah may increase his intimacy with (either hope or gratitude) and his joy (surūr) in the face of his good opinion (ḥusn al-ẓann) of Allah's mercy. In this way, Allah lays the foundation of khawf (fear) and rajāʾ in his heart. These two feelings drive the servant to avoid (bad feelings and attitudes), thus becoming two actions of the heart. When heedlessness (ghafla) befalls such a heart, ishfāq (the anxiety arising from seeing the consequences of this heedlessness) leads the servant to khawf, and the servant becomes fearful of the stages of the Hereafter. (Bed, 35)
Obedience (ṭāʿa) is the path to salvation, and knowledge (ʿilm) is the guide on this path. The essence (foundation) of obedience is warāʿ (scrupulousness), the essence of warāʿ is taqwa (God-consciousness), the essence of taqwa is self-reckoning (muḥāsaba al-nafs), and the foundation of self-reckoning is khawf and rajāʾ. The guide for self-reckoning is knowledge. (Riʿāya, 12)
How does one attain khawf and rajāʾ? The answer is: as much as Allah's promise (waʿd) regarding Paradise and blessings, and His warning (waʿīd) regarding Hell and punishment, as well as ...