Sahih al-Bukhari 4529
صحيح البخاري#4529SahihNarrated Al-Hasan:The sister of Ma'qil bin Yasar was divorced by her husband who left her till she had fulfilled her term of 'Iddat (i.e. the period which should elapse before she can Remarry) and then he wanted to remarry her but Ma'qil refused, so this Verse was revealed:-- "Do not prevent them from marrying their (former) husbands
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: 65:52