Book of Divorce
(1) Divorce is permissible when there is a genuine need; it is disliked when no such need exists; it is recommended under compelling necessity; it becomes obligatory in the case of an unfulfilled oath of abstinence (ilaʾ); and it is forbidden when carried out in an innovated manner (bidʿah).

A divorce is valid when pronounced by the husband—even if he is only a discerning minor who understands what he is saying—or by a judge acting on behalf of a husband who has taken ilaʾ. It is not valid (2) when issued by someone whose reason has departed, except for a sinful drunkard, whose divorce does take effect; nor by a person who is coerced through wrongful threats—such as punishment to himself or his child, the seizure of property (3) that would harm him, or intimidation by someone capable of carrying out the threat—so that he divorces merely in compliance with the coercer.

An agent appointed by the husband has the same authority as the husband himself: he may pronounce a single divorce whenever (4) he wishes if no time limit has been set for him. The same rule applies to the wife when her husband has delegated that authority to her.

Section
The Sunnah for one who intends to divorce is to issue a single pronouncement while the wife is in a state of purity during which he has not had intercourse with her, and then to leave her.

Uttering three divorces at once is forbidden unless each pronouncement is separated by a new contract or a reinstatement during the waiting period. If he divorces a woman he has consummated the marriage with while she is menstruating, or during a purity in which he had intercourse with her, that is an innovated form; it nevertheless counts, and it is recommended that he take her back.

There is neither Sunnah nor innovation in the case of a pre-pubescent girl, a post-menopausal woman, a wife whose marriage has not been consummated, or a woman whose pregnancy is clearly evident.