According to the Sufis, a person's entry into the Sufi life is a kind of "second birth." With this birth, two kinds of purification are necessary: material purification and spiritual purification. The first refers to the major ritual ablution (ghusl), the regular ablution (wuḍūʾ), and the cleanliness of one's clothing and appearance; the second refers to inner purification, that is, the purification of thought and spirit (ruh). The first step to realize this second purification is to turn towards the Real (al-Ḥaqq) and the truth (ḥaqīqa) by abandoning errors and sins. This is accomplished through tawba (repentance). In fact, the literal meaning of the word tawba is "to return": to return from falsehood to truth, from sin to good deeds, from Satan to Allah. In short, tawba is sincere remorse felt for one's sins.
Tawba is one of the subjects that the Qur'an especially emphasizes. The Qur'an not only informs us that people with many sins should not despair of Allah's mercy and compassion—"Say: O My servants who have transgressed against themselves [by sinning], do not despair of the mercy of Allah. Indeed, Allah forgives all sins. Indeed, it is He who is the Forgiving, the Merciful" (al-Zumar, 39:53)—and that, except for associating partners with Allah (shirk), it is possible to have all sins forgiven through tawba, but also adds that Allah loves those who repent: "Indeed, Allah loves those who are constantly repentant and loves those who purify themselves" (al-Baqara, 2:222). The Qur'an also praises those who perform tawba and seek forgiveness (istighfār) at the time of dawn, in places and times where no one sees them: "The patient, the true, the obedient, those who spend [in the way of Allah], and those who seek forgiveness before dawn" (Āl ʿImrān, 3:17). The Prophet (peace and blessings be upon him) also stated that he frequently performed tawba and sought forgiveness.
When one looks at the life stories and legends (menāqib) of the Sufis, it is seen that very different things have led them to tawba. A book that is read, a conversation that is listened to, a verse (āya) that is heard, a dream that is seen, or even showing respect to a piece of paper found on the road on which the name of Allah is written...
When asked what tawba is, Junayd answered: "It is to forget the sin"; Tustarī answered: "It is not to forget the sin." Junayd continues: "Tawba has three meanings: The first is remorse, the second is to make a firm decision not to repeat what Allah has forbidden, and the third is to strive to redress the wrongs that have been committed."
The point that is especially emphasized is to be sincere in tawba and not to commit major errors that would require tawba again. Yahyā b. Muʿādh draws attention to this: "A sin committed after tawba is uglier than seventy sins committed before tawba."
The person who realizes the "second birth" is in need of special attention. The period of Sufi life surrounded by these special conditions is known as "khalwa" (spiritual retreat), and is also referred to as "uzla" (seclusion).