To abandon sins and (in the future, that is, in what is to come) not to return to anything similar to the sins one has committed. Then, it is necessary to satisfy adversaries by fulfilling their rights and to obtain their contentment for the injustices done to them (to seek their pardon). If one is unable to do so, one should resolve in one's qalb (the heart) to leave this state as much as possible. In this state, one turns to Allah, pleading for exoneration from this liability (barāʾat al-dhimma, release from obligation) and making dua (supplication) for one's adversaries. (Nebhāni, I, 249)
Tawba-i ināba (ināba tawba) is the servant's tawba (repentance) out of fear of Allah's punishment.
Tawba-i istijāba (istijāba tawba) is to make tawba out of shyness before Allah's generosity toward you. Abū Ḥusayn al-Nūrī said: Tawba is to repent from everything other than Allah.
Qushayrī says: Abū'l-Qāsim al-Junayd also said: One day I entered the presence of Sari al-Saqaṭī and saw a change in his face. I asked, "What happened to you?" He said: "A young man came to me and asked what tawba is. I told him, 'It is not to forget your sin.' He objected and said, 'Rather, tawba is to forget your sin.' So I said, 'In my view, the truth is as the young man said.' (And then Junayd) said: 'In the state of suffering (jafāʾ), He transferred me to the state of loyalty (wafāʾ). To remember suffering in the state of felicity (ṣafāʾ) is itself suffering.' (Upon this, Sari fell silent.)
Likewise, Sahl ʿAbdallāh (al-Tustarī) gave the same answer as Sari. Abū Naṣr al-Sarrāj (al-Tūsī) says: Sahl indicated the states of murīds (aspirants, disciples) who sometimes act in their own favor and sometimes against themselves. Junayd, however, indicated the tawba of the verifiers (muḥaqqiqūn). They do not remember their sins because the majesty of Allah and constant dhikr (remembrance of God) have overcome their qalb. (Nebhāni, I, 250)
Tawba has preliminaries, signs, fruits, boundaries, and conditions. The first of its preliminaries is to awaken the qalb from the sleep of heedlessness so that the servant sees the evil state he is in; to avoid Allah's anger and the pain of His punishment; and to remember one's weakness in bearing the severity of punishment. This leads a person to tawba.
Among the signs of (tawba) are: abandoning bad friends and close associates, feeling discomfort with them; loving solitude; speaking little; ceasing to immerse oneself in the company of people; avoiding useless activities; protecting the body from bad actions; increasing worship; persisting in dhikr; lowering the head; reducing one's gaze (to prevent the eyes from falling upon the forbidden); bodily weakness; weeping eyes; a saddened qalb; grieving over the days spent, the excesses in opposing divine commands, and the precious moments of one's life wasted in pursuit of the desires of the nafs (the lower self), actions that entail opposition to divine commands, and base shahwa (passions); constant weeping; supplicating day and night, yearning to have one's repentance accepted or to renew a broken covenant. (Nebhāni, I, 251)
According to the consensus of the Sufi community, except for the people of ilḥād (heresy) and bidʿa (innovation), the conditions of tawba for the mu'min (believer) have been accepted by consensus. These conditions are: the servant's remorse for what he has done in opposition to divine commands; to immediately and without hesitation abandon that act at that moment, without turning to anything else.