´It was narrated from 'Ubadah bin Samit from Rubai' bint Mu'awwidh bin 'Afra'.:` He said: "I said to her: 'Tell me your Hadith.' She said: 'I got Khul' from my husband, then I came to 'Uthman and asked him: "What waiting period do I have to observe?" He said: "You do not have to observe any waiting period, unless you had intercourse with him recently, in which case you should stay with him until you have menstruated." In that he was following the ruling of the Messenger of Allah (ﷺ) concerning Maryam Maghaliyyah, who was married to Thabit bin Qais and she got Khul' from him.' "
Explanation & Benefits
Maulana Ataullah Sajid
Benefits and Issues:
➊ Although the outward form of khul‘ is similar to divorce (talaq)—that is, the man divorces the woman at her request—in reality, it is an annulment (faskh) of the marriage. Therefore, its waiting period (‘iddah) is not three menstrual cycles, but rather one menstrual cycle.
➋ The waiting period of one menstrual cycle after khul‘ is for the purpose of ensuring the womb is free (istibra’ al-rahim), meaning its objective is to ascertain whether the woman is pregnant or not. The occurrence of one menstrual cycle makes this clear. If menstruation does not occur, it means she is pregnant; therefore, she cannot marry another man until the child is born.
Source: Commentary on Sunan Ibn Mājah by Mawlānā ‘Atā’ullāh Sājid, Page: 2058