Wa `alaykum as-Salamu wa rahmatullahi wa barakatuh.
In the Name of Allah, Most Gracious, Most Merciful.
All praise and thanks are due to Allah, and peace and blessings be upon His Messenger.
Dear questioner, we would like to express our appreciation to you for the great confidence you repose in us and for this apparent keenness on understanding the teachings of Islam.
Regarding the question of the `Iddah (waiting period) of a woman separated by Khul`, here is the fatwa issued by Sheikh Muhammad Saleh Al-Munajjid, a prominent Saudi scholar and lecturer, in this regard,
Khul`, in principle, can only occur at the request of the wife and with the husband’s subsequent agreement. `Iddah is obligatory upon every woman who leaves her husband or whose husband leaves her, whether the cause of such separation is Talaq (divorce), annulment of the marriage, or the death of the husband, except the case when the divorce occurs before the marriage has been consummated as in such a case a woman does not have to observe `Iddah. Allah the Almighty says, “O you who believe! When you marry believing women, and then divorce them before you have sexual intercourse with them, no `Iddah (waiting period) have you to count in respect of them” (Al-Ahzab 33:49)
With regard to the `Iddah following Khul`, the correct opinion is that it is one menstrual cycle, as is indicated by the Sunnah. It was narrated by Ibn `Abbas that the wife of Thabit ibn Qays ended her marriage to her husband by means of Khul` at the time of the Prophet (peace and blessings be upon him). The Prophet (peace and blessings be upon him) commanded her to observe a waiting period of one menstrual cycle. (At-Tirmidhi and Abu Dawud)
Ibn al-Qayyim (may Allah shower him with His mercy) commented,
The prophetic command to the woman who ended her marriage through Khul` to observe a waiting period of one menstrual cycle indicates two rulings:
The first is that she does not have to wait for three menstrual cycles, rather one menstrual cycle is sufficient. Besides being clearly the prophetic injunction in this regard, it was also the view of `Uthman ibn ‘Affan, `Abd-Allah ibn ‘Umar ibn al-Khattaab, Ar-Rubayyi` bint Mu`awwadh and her paternal uncle, who was one of the greatest Companions. We do not know of anyone who held a different opinion from among them. Al-Layth ibn Sa`d narrated that Nafi`, the freed slave of Ibn `Umar, heard Ar-Rubayyi` bint Mu`awwadh ibn `Afra’ telling `Abd-Allah ibn `Umar (may Allah be pleased with him) that she had ended her marriage to her husband by way of Khul` at the time of `Uthman ibn `Affan and that her paternal uncle came to `Uthman ibn `Affan saying, “The daughter of Mu`awwadh ended her marriage by way of Khul` today. Should she move [from the marital house]?” `Uthman said, “She should move and there is no inheritance between them. She does not have to observe `Iddah, but she should not remarry until one menstrual cycle has passed, lest she be pregnant.” `Abdullah ibn ‘Umar then said, “‘Uthman was the best of us and the most knowledgeable.”
This view was also adopted by Ishaq ibn Raahawayh and Imam Ahmad, according to one report narrated from him. It was also the view favored by Shaykh al-Islam Ibn Taymiyah.
Those who supported this view said: This goes in accordance with the principles of the Shari`ah. The `Iddah [in the case of divorce] was made three menstrual cycles in order to lengthen the time during which the husband may take back his wife, so that the husband should have enough time to rethink about the matter and be able to take his wife back during this time. But in the case of Khul` the wife is not going back and the purpose is simply to find out whether she is pregnant or not. Hence, one menstrual cycle is sufficient.
Almighty Allah knows best.