…Do not draw near any acts of lewdness, whether openly or in secret...Whether openly refers to that which it has been forbidden to do with the external bodily members. Or in secret means the persistence (iṣrār) in committing that act, and this is of two kinds: the first is that a person commits a sin and persists in committing it; the other is that he persists in sin through desiring it in his heart, but he is not able to do it when he finds the opportunity because of a weakness in his bodily members, even though he is intent upon doing it. This is one of the most serious forms of persistence.Then Sahl said:Whoever eats what is permissible (ḥalāl) with gluttony is persistent (muṣirr), and whoever preoccupies himself with what the morrow may bring before the morrow arrives is persistent.He was asked about the prophets Â, regarding whether they thought about that which did not concern them. He replied:An act with their bodily members was allowed to them, considering that they repented to God, Exalted is He, afterwards, let alone a mere thought.He was asked, ‘Is there a form of worship for the heart, which God requires of it, other than that which is performed by the bodily members?’ He replied, ‘Yes, it is the tranquil repose (sukūn) of the heart [in God].’ Then he was asked, ‘Is such tranquil repose [in God] obligatory (farḍ) or the knowledge by which it is attained?’ He answered, ‘It is a [kind of] knowledge, which I am calling tranquil repose, and that tranquil repose [in God] leads to certainty (yaqīn). Furthermore, tranquil repose accompanied with certainty is an obligation (farīḍa).’His words, Exalted is He:
