One who affirms His fardāniyya (uniqueness), pre-eternity, and post-eternity has truly confirmed Him in the real sense. (Ādāb, 55)
The essence of taqwa (God-consciousness) is in the qalb (the heart). Taqwa is a shield that protects from doubt, shirk (associating partners with God), kufr (disbelief), nifāq (hypocrisy), and riya (ostentation). (Bayān, 54)
Sahl al-Tustarī says: Taqwa is merely observing the aḥwāl (spiritual states). Its meaning is this: A person who finds tranquility with Allah and delights in this state should not fear anyone other than Allah. (Taʿarruf, 69)
The essence of taqwa is to keep away from prohibited things and to oppose the nafs (the lower self). (Those who walk this path) realize yaqīn (certainty) to the extent that they distance themselves from the pleasures of the nafs. (Taʿarruf, 70)
Taqwa is the servant’s avoidance of everything other than Allah. Sahl says: Whoever wants his taqwa to be sound should abandon all sins! Nasrābādhī also says: Whoever clings to taqwa desires to renounce the world. (Qushayrī, 56)
Taqwa is used in three senses in the Qur'an: The first is the meaning of khashya (awe) and hayba (reverent fear). Allah says: "So fear only Me" and "Fear a Day when you will be returned to Allah" (al-Baqara 2:281).
The second meaning is obedience and worship. Allah says: "O you who have believed, fear Allah as He should be feared" (Āl ʿImrān 3:102). In the tafsir (Qur'anic exegesis) of this verse, Ibn ʿAbbās says: Obey Allah as He should be obeyed. Mujāhid also said: This means to obey and not to disobey.