Hadith 2451
Narrated Hafsah, Ummul Muminin: The Messenger of Allah ﷺ used to fast three days every month: Monday, Thursday and Monday in the next week.
Hadith 2452
Narrated Umm Salamah, Ummul Muminin: Hunaydah al-Khuzai reported on the authority of her mother who said: I entered upon Umm Salamah and asked her about fasting. She said: The Messenger of Allah ﷺ used to command me to fast three days every month beginning with Monday or Thursday.