Sahih al-Bukhari 5251
صحيح البخاري#5251SahihNarrated `Abdullah bin `Umar:that he had divorced his wife while she was menstruating during the lifetime of Allah's Messenger (ﷺ) . `Umar bin Al-Khattab asked Allah's Messenger (ﷺ) about that. Allah's Messenger (ﷺ) said, "Order him (your son) to take her back and keep her till she is clean and then to wait till she gets her next period and becomes clean again, whereupon, if he wishes to keep her, he can do so, and if he wishes to divorce her he can divorce her before having sexual intercourse with her; and that is the prescribed period which Allah has fixed for the women meant to be divorced
Scholarly Authentication
We show the most cautious grade (weakest-wins) as the overall label. Individual scholars graded it as follows:
Every narration in Sahih al-Bukhari is accepted as Sahih (authentic) by the established status of the book.
In-book reference: 68:1