Question: What is the ruling regarding fasting the 15th day of the month of Sha’baan, and is it permissible to fast the ‘day of doubt’ – at the end of the month? [Please] provide us with a ruling, [and] may you be rewarded.
Response: All Praise is [indeed] due to Allaah [alone], Lord of the worlds, and I send prayers and salutations upon our Prophet Muhammad, and upon his family and all his companions.
And I ask Allaah (Subhaanahu wa Ta’aala) to inspire us [to respond] with what is correct in speech and action.
[Regarding] fasting the 15th [day] of the month of Sha’baan, [then] there are ahaadeeth about its virtue, and the virtue of standing the night [in prayer] – the night of the 15th, as well as the virtue of the 15th day [itself] – however, these ahaadeeth have [all] been classified as weak by most of the people of knowledge.
And [regarding] the weak ahaadeeth proof cannot be established with them, particularly in practical issues.
And based upon that, then to single out the 15th day of Sha’baan by fasting and to single out the night of the 15th of Sha’baan by standing [in prayer] is not legislated due to there not being any authentic ahaadeeth on this [issue] – according to most of the people of knowledge.
And [so], nothing authentic exists from the Prophet ﷺ, and nor from his companions about its virtue.
As for a person fasting the three full moon days in the month of Sha’baan – and they are the 13th, 14th and 15th days – then there is no harm in that, because it is recommended for a person to fast 3 days of every month, and it is best to do so during these 3 days; the 13th, 14th and 15th.
And it has been authentically reported that the Prophet ﷺ that he said:
And as for fasting the ‘day of doubt’ – and it is the 30th day of Sha’baan; if it is the night, the night of the 30th is cloudy, or there is something [in the sky] preventing sighting of the moon, then it is prohibited [to fast the following day], because of the statement of ‘Ammaar ibn Yaasir (radhi-yAllaahu ‘anhu):
“Whoever fasts on the day concerning which there is doubt then he has disobeyed Abul-Qaasim ﷺ.” [transmitted by at-Tirmidhee and an-Nasaa.ee]
And [it has been transmitted] in Saheeh al-Bukhaaree and Saheeh Muslim, that the Prophet ﷺ said: