From Reliance of the Traveler, a known Islamic manual on Sharia law, p. 540
mlO.12 When a husband notices signs of rebelliousness in his wife (nushuz. dis: p42) (0; whether in words, as when she answers him coldly when she used to do so politely, or he asks her to come to bed and she refuses, contrary to her usual habit; or whether in acts, as when he finds her averse to him when she was previously kind and cheerful). he warns her in words (without keeping from her or hitting her, for it may be that she has an excuse). The warning could be to tell her, “Fear Allah concerning the rights you owe to me,” or it could be to explain that rebelliousness nullifies his obligation to support her and give her a turn amongst other wives, or it could be to inform her, “Your obeying me [def: (3) below] is religiously obligatory”). If she commits rebelliousness, he keeps from sleeping (and having sex) with her without words, and may hit her, but not in a way that injures her, meaning he may not (A: bruise her,) break bones, wound her, or cause blood to flow. (It is unlawful to strike another’s face.) He may hit her whether she is rebellious only once or whether more than once, though a weaker opinion holds that he may not hit her unless there is repeated rebelliousness.
(N: To clarify this paragraph, we mention the following rulings:
(1) Both man and wife are obliged to treat each other kindly and graciously.
(2) It is not lawful for a wife to leave the house except by the permission of her husband, though she may do so without permission when there is a pressing necessity. Nor may a wife permit anyone to enter her husband’s home unless he agrees, even their unmarriageable kin. Nor may she be alone with a nonfamily-member male, under any circumstances.
(3) It is obligatory for a wife to obey her husband as is customary in allowing him full lawful sexual enjoyment of her person. It is obligatory for the husband to enable her to remain chaste and free of want for sex if he is able. It is not obligatory for the wife to serve her husband (dis: w45.1); if she does so, it is voluntary charity.
(4) If the wife does not fulfill one of the above-mentioned obligations, she is termed “rebellious” (nashiz), and the husband takes the following steps to correct matters:
(a) admonition and advice, by explaining the unlawfulness of rebellion, its harmful effect on married life, and by listening to her viewpoint on the matter;
(b) if admonition is ineffectual, he keeps from her by not sleeping in bed with her, by which both learn the degree to which they need each other;
(c) if keeping from her is ineffectual, it is permissible for him to hit her if he believes that hitting her will bring her back to the right path, though if he does not think so, it is not permissible. His hitting her may not be in a way that injures her, and is his last recourse to save the family;
(d) if the disagreement does not end after all this, each partner chooses an arbitrator to solve the dispute by settlement, or divorce.)