The White Days, known in Arabic as Ayyam al-Bid (the “bright” or “white” days), are the 13th, 14th, and 15th of every Hijri month. They are called “white” because they are the nights of the full moon – when the moon’s light makes the nights bright. Fasting on these three days each month is a strongly emphasized voluntary practice of the Prophet Muhammad (peace be upon him).

Abu Hurairah reported: “My close friend [the Prophet, peace be upon him] advised me with three things, which I will not abandon as long as I live: fasting three days of every month, the Duha prayer, and praying witr before sleeping.” (Sahih al-Bukhari 1981. Abu Dharr reported that the Prophet (peace be upon him) was specific about which three days: “O Abu Dharr, if you fast three days of each month, then fast the 13th, 14th, and 15th.” (Jami’ at-Tirmidhi 761).

The reward is generous: fasting three days of every month is, in effect, fasting the equivalent of a full year, since each good deed is rewarded ten times. The Prophet (peace be upon him) said: “Whoever fasts three days of every month, that is fasting for a lifetime,” and Allah then revealed the verse: “Whoever brings a good deed will have ten times the like thereof.” (Surah al-An’am 6:160; see also Sahih al-Bukhari).

The White Days can be fasted in any Hijri month, including the sacred months, with two practical caveats. They are not fasted in Dhul-Hijjah’s 13th, because the 11th-13th of Dhul-Hijjah are the Days of Tashriq, on which fasting is prohibited (Sahih Muslim 2561). And they are subsumed by the obligation of Ramadan‘s fast for anyone observing the month of fasting in Ramadan.

For Muslims, the White Days are a simple, recurring rhythm of monthly worship – three days of fasting, three nights of the full moon – that ties the worshipper to the lunar calendar and to the Sunnah of the Prophet (peace be upon him). The Islamic Calendar on this site marks the White Days in every month so they can be tracked, added to a subscription calendar, or planned for in advance.