Sunan an-Nasa'i 2365
سنن النسائي#2365SahihIt was narrated that Umm Salamah said:"The Messenger of Allah used to fast three days of every month: the Monday and Thursday of the first week and the Monday of the following week
Scholarly Authentication
We show the most cautious grade (weakest-wins) as the overall label. Individual scholars graded it as follows:
Abu GhuddahHasan
Al-AlbaniHasan
Zubair Ali ZaiSahih
In-book reference: 22:276