Sunan an-Nasa'i 3526
سنن النسائي#3526SahihIt was narrated from 'Aishah that the Prophet said:"It is not permissible for a woman who believes in Allah and the Last Day to mourn for more than three days, except for her husband
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 ZaiSahih
In-book reference: 27:138