Sunan an-Nasa'i 2415
سنن النسائي#2415SahihHunaidah Al-Khuza'i said:"I entered upon the Mother of the Believers and heard her say: 'The Messenger of Allah used to fast three days of each month: The first Monday of the month, then Thursday, then the following Thursday
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 ZaiIsnaad Hasan
In-book reference: 22:326