´It was narrated that 'Abdullah bin Masud said:` "The Messenger of Allah used to fast three days in the middle of every month, and he rarely did not fast on Friday."
Hadith ReferenceSunan an-Nasa'i / The Book of Fasting / Hadith: 2370
Hadith Gradingالألبانی:حسن | زبیر علی زئی:إسناده حسن