His statement: “And if she is detained, even wrongfully.” Detention may either be for a legitimate claim from which she is able to free herself, or otherwise. If it is for a legitimate claim, and she is at fault and able to free herself, then there is no doubt that her maintenance is forfeited. For example, she may owe someone a debt, while being financially able to pay it and not insolvent; he then brings a complaint against her and she is lawfully detained. Her maintenance is forfeited, because she could free herself if she wished.
But if she is detained wrongfully—for example, if she is accused of something while innocent—the authoritative position in the madhhab is that her maintenance is forfeited. The correct view, however, is that it is not forfeited, because her husband’s inability to have intimacy with her is not due to anything on her part. It is therefore like his inability to have intimacy with her because of illness or the like.
His statement: “Or she is disobedient.” Linguistically, nushūz (marital disobedience) derives from nashaz, meaning elevation. In the Sacred Law, it means a wife’s disobedience to her husband regarding what is obligatory upon her. This includes her refusing when he calls her to his bed, refusing when he forbids her from going out, or refusing when he requires her to observe the prescribed Islamic hijab: that a woman cover her entire body, including her face, head, and hands.
His statement: “Or she observes a voluntary fast without his permission”—even if that fast is connected to an obligatory act, such as fasting six days of Shawwal.
Fasting may be unrestricted, restricted to a particular time, or connected to an obligatory act. The type connected to an obligatory act includes fasting six days of Shawwal. The type restricted to a particular time includes the fast of the Day of Arafah and the Day of Ashura; fasting three days of every month may also be placed in this category. Unrestricted fasting comprises all other fasts not tied to a specific time. Thus, if a woman voluntarily observes any of these categories of fast without her husband’s permission, she is not entitled to maintenance.