Sunan an-Nasa'i 3527
سنن النسائي#3527SahihIt was narrated from Zainab bint Abi Salamah that Umm Habibah said:"I heard the Messenger of Allah say this on this Minbar: 'It is not permissible for a woman who believes in Allah and His Messenger to mourn for anyone who dies for more than three days, except for a husband, (for whom the mourning period is) four months and ten days
Scholarly Authentication
We show the most cautious grade (weakest-wins) as the overall label. Individual scholars graded it as follows:
Abu GhuddahSahih
Al-AlbaniSahih
Zubair Ali ZaiHasan
In-book reference: 27:139