We say: The Sufi is the one who is always occupied with the purification (tasfiya) of the qalb (the heart). By purifying the qalb from the impurities of the nafs (the lower self), he cleanses every moment from turbidity. In this purification, his constant state of iftiqār (neediness before God) towards his Lord assists him. As a result, the continuity of iftiqār purifies him from all turbidity. If the nafs is stirred and one of its attributes emerges, he immediately perceives this with deep basīra (spiritual insight), and at once seeks refuge in Allah from the nafs. By persisting in purification, he lives in the state of jun (spiritual presence). When the nafs is stirred, the state of distinction (farq) appears, and separation and turbidity arise. However, when his Lord rules over his qalb, he, by means of his qalb, gains mastery over his nafs.
Calling the Sufis 'Sufi' because they wore wool (sūf) is a judgment based on their outward aspect. To describe them by attributing to them any of the spiritual states (ḥāl) or stations (maqām) is a judgment based on their inward aspect. The judgment based on their outward aspect is more appropriate and preferable. The view that names them 'Sufiyya' by associating them with their woolen garments is more fitting for humility and closer to the truth.
(According to one view) they are called Sufiyya because, by directing their zeal (ghayra) and care with their qalb and hearts to Allah and to being present before Him at all times, they take the foremost rank in the presence of Allah.
It is also said that this name was given to the Sufiyya in reference to the Aṣḥāb al-Ṣuffa, the poor and emigrants who lived around the Prophet (peace and blessings be upon him) and under his guidance during his time.
The Sufi is in the station of the mufarridūn (those singled out), about whom the Messenger of God (peace and blessings be upon him) said: 'They are those who are deeply devoted to the dhikr (remembrance of God) of Allah. Dhikr has lifted their burdens from them. Thus, they will come to the Resurrection (qiyāma) lightened.' (Tirmidhi, Duʿāʾ, 128). The mutaṣawwif is the one who, in his spiritual journey, reaches the point where the qalb settles in the dhikr of Allah, attains vigilance (murāqaba) with his qalb, and tastes the delight of contemplating Allah's gaze. The Sufi-mutaṣawwif-mustaswif/Sufiyya is the one who has reached the station of the sāʾir (spiritual traveler). The Sufi is the one who possesses witnessing (mushāhada) where the ruh (the spirit) has found rest. The mutaṣawwif is the one who possesses murāqaba where the qalb has found rest.
Jaʿfar Huldi said: I asked Abū'l-Qāsim Junayd: 'Is there a difference between ikhlas (sincerity) and ṣidq (truthfulness)?' He replied: 'Yes, ṣidq is the root and the first, ikhlas is the branch and follows ṣidq. The second always follows the first.' He continued: 'There is a difference between them. For ikhlas only arises after one begins to act. Ikhlas is to make ikhlas pure, to be pure (in intention) in this matter. The defined ikhlas is the state of the Malāmatiyya, while the striving to purify ikhlas is the state of the Sufis. To possess pure ikhlas in the act of purifying ikhlas is only possible when ikhlas itself is made pure.'