Reference: Fataawa Ramadhaan – Volume 2, Page 723, Fatwa No.730
Fataawa as-Siyaam – Page 101
Question: What is the day of doubt and is it permissible to fast on that day?
Response: The day of doubt is the 30th day of Sha’baan, and it is not permissible to fast on this day as it has been related by ‘Ammaar ibn Yaasir (radhi-yAllaahu ‘anhu) who said:
«Whoever fasts on the day concerning which there is doubt has disobeyed Abul-Qaasim ﷺ», [transmitted by at-Tirmidhee and an-Nasaa.ee]
