Third: sexual intercourse and its preliminaries are not permitted during it, unlike fasting, during which the preliminaries to intercourse are permissible. She would therefore prevent her husband from many things.
Thus, if she enters ihram for a voluntary Hajj without his permission, her maintenance is forfeited. Yet this will generally not occur, since she will not travel to Mecca without his permission. The same applies if she undertakes a voluntary Umrah. The governing principle is that if a woman engages in an act of worship that prevents her husband from full conjugal enjoyment, her maintenance is forfeited.
If she voluntarily performs a prayer without his permission, should we say that her maintenance is forfeited, or should we say that its duration is brief? The apparent meaning of the author’s words is that prayer is not like fasting and Hajj, because its time is short.
It is understood from his words, “without his permission,” that if she does any of this with his permission, her maintenance is not forfeited, since he permitted her and thereby relinquished his own enjoyment.
His statement, “or enters ihram due to a vow to perform Hajj,” means that her maintenance is forfeited, because she herself was the cause of making it obligatory upon herself.
For example, a woman vows to perform Hajj, and so she is required to fulfil her vow. She says to her husband, “I have vowed to perform Hajj this year,” and he says, “Do not perform Hajj.” If she then performs Hajj, she is not entitled to maintenance, because she was the cause of its becoming obligatory upon her.
But if he permits her to make the vow, then according to the established legal school she is not entitled to maintenance. The correct view, however, is that she is entitled to it. For example, she says, “If Allah cures me of my illness, or cures my child of his illness, I would like to vow to Allah Most High that I will perform Hajj.” He replies, “There is no objection.” In that case, he is obliged to maintain her, because he permitted her to make the vow.