Sunan Abi Dawud 2437
سنن أبي داود#2437SahihNarrated One of the wives of the Prophet: Hunaydah ibn Khalid narrated from his wife on the authority of one of the wives of the Prophet (ﷺ) who said: The Messenger of Allah (ﷺ) used to fast the first nine days of Dhul-Hijjah, Ashura' and three days of every month, that is, the first Monday (of the month) and Thursday
Scholarly Authentication
We show the most cautious grade (weakest-wins) as the overall label. Individual scholars graded it as follows:
Al-AlbaniSahih
Muhammad Muhyi Al-Din Abdul HamidSahih
Zubair Ali ZaiIsnaad Sahih
In-book reference: 14:125