Case: There is no harm to practice Khul` during menstruation or when the wife is pure because the forbiddance of divorcing one's wife during menstruation is done to stop the harm that will happen due to the long period of the waiting period.
However, Khul` is done in the first place to remove the harm done by the husband due to his bad manner or because she does not like him which is more harmful than waiting for a long time. So, it is permissible to remove the bigger harm with the lesser one; therefore the Prophet (peace be upon him) did not ask the wife who asks for Khul` about her conditions.
And because she owns herself by asking for Khul`, so there is a benefit in hastening separation to remove the evil between them unlike the case in revocable divorce which has no benefit in hastening it before its time but it will be harmful.
It was said: Khul` is a type of divorce in a time when the husband does not desire her or in no need to her unlike the divorce in the time of desire which is not applied except when there is a need. (1)
Case: It is permissible to practice Khul` with less or more than the dower a husband paid if they agree to that because of Allah's Saying: "Then there is no sin on either of them if she gives back (the Mahr or a part of it) for her Al Khul` (divorce)."
Ar-Rubayy` bint Mu`awwidh said: I asked for Khul` for less than the plait of my hair. So, `Uthman ibn `Affan (may Allah be pleased with him) permitted Khul` for that and no one of the Companions objected, so it is consensus because it is the view of `Uthman, Ibn `Umar, and Ibn `Abbas (may Allah be pleased with him) and the view of most scholars.
Case: Is it permissible to practice Khul` without any compensation?
Scholars differed into two views: The first is the view of Imam Malik and one of the two narrations of Imam Ahmad that Khul` is invalid without compensation because it is an interruption of marriage, so it is permissible for no compensation such as divorce. Moreover, the origin of the permissibility of Khul` is that a wife does not have the desire to continue the marital relationship with her husband and wants to separate from him. So, she asks for Khul` and when he accepts, Khul` is valid even if it is done without compensation.
The second view is: Khul` must be done for a compensation which is the view of Abu Hanifah, Al Shafi`y, and one of the two narrations of Imam Ahmad because when Khul` is a kind of annulment, the husband does not have the power to annul marriage except by her choice. Likewise, if the husband says: I have annulled the marriage without having the intention of divorce, nothing will happen but if there is a ransom, it will be a bargain. If we say that Khul` is a type of divorce, it is not explicit but it is implicit and this kind cannot activate divorce without an intention or a ransom which will replace intention if it exists.
(1) In addition to the main references, see Majmu` Al Fatawa 33/21.