Fasting the White Days (Ayyam al-Beed)
Every month, in the middle of the Islamic calendar, there are three days that shine a little brighter than the rest. They are the thirteenth, fourteenth and fifteenth of the lunar month — the days around the full moon — and the Messenger of Allah ﷺ commanded his followers to fast them. He called them the days of the white nights, Ayyam al-Beed, and he attached a promise to them that is hard to forget: three short days, kept month after month, carry the weight of fasting the entire year.
This is not a heavy or complicated devotion. It asks for no special season, no travel, and no waiting for a particular month to arrive. The white days come around with every moon, and the one who keeps them builds a rhythm of fasting that runs quietly through the whole of life. In this article we will look at what the authentic texts actually say about these days: the command itself, the exact dates, the reasoning the Prophet ﷺ gave, and the place this simple fast holds among the other types of fasting taught in the Sunnah.
1. What Are the White Days?
The white days are the thirteenth, fourteenth and fifteenth days of each month of the Islamic lunar calendar. Their name comes from their nights. In the middle of the lunar month the moon is full, its light is at its strongest, and the nights are bright — white with moonlight. The days that follow those luminous nights took the same name: the white days, Ayyam al-Beed.
Because the Islamic calendar is lunar, these dates move through the seasons of the solar year. In one year the thirteenth of a month may fall in the long days of summer; in another cycle it falls in the short days of winter. What never changes is the pattern: three days, in the middle of every month, marked out by the Prophet ﷺ for fasting.
It helps to remember that the dates are counted by the moon, not by the Gregorian calendar most of us use for work and school. The thirteenth, fourteenth and fifteenth are days of the Hijri month. A person who wants to keep this fast simply follows the Islamic date — the same date used for Ramadan and the two Eids — and watches for the middle of each month as it comes.
2. The Prophet’s Command: Fast the Thirteenth, Fourteenth and Fifteenth
The command itself is recorded with its dates spelled out. Qatadah Ibn Malhan al-Qaysi reported:
“The Messenger of Allah (ﷺ) used to command us to fast the days of the white (nights): thirteenth, fourteenth and fifteenth of the month.” (Sunan Abu Dawud 2449 — Sahih)
Notice three things in this short narration. First, the words describe a standing command, not a single occasion: the Messenger of Allah ﷺ “used to command us” — this was his regular instruction to his companions. Second, the dates are not left vague. He did not merely say “fast in the middle of the month”; he named the thirteenth, the fourteenth and the fifteenth. Third, the narration tells us what these days are called in his own words: the days of the white nights.
And the narration does not stop at the command. It carries the Prophet’s ﷺ own description of what this fast amounts to:
“This is like keeping perpetual fast.” (Sunan Abu Dawud 2449 — Sahih)
Three days — “like keeping perpetual fast.” That single sentence is the heart of this practice. The Prophet ﷺ did not present the white days as a small extra for the especially devout. He presented them as the attainable form of a much greater thing: the fast of a lifetime, folded into three days a month.
3. Three Days Every Month: The Wider Teaching
The white days are the specified dates, but they sit inside a wider teaching that the Prophet ﷺ explained on another occasion, when the question of fasting patterns was put to him directly. Abu Qatada reported that a man asked the Messenger of Allah ﷺ how he fasted, and when Umar saw the Prophet’s ﷺ annoyance at the question, he calmed the moment and began asking instead about the different ways people fast. About the one who fasts perpetually — every day without break — the Prophet ﷺ said:
“He neither fasted nor broke it” (Sahih Muslim 1162a — Sahih)
Perpetual fasting, fasting without pause, was not praised. It overshoots what Allah asks and what the body can carry. Then Umar asked about fasting on alternate days — one day fasting, one day not — and the Prophet ﷺ answered:
“That is the fast of David (peace be upon him).” (Sahih Muslim 1162a — Sahih)
Then, after these exchanges, the Messenger of Allah ﷺ gave the teaching that holds the middle path:
“Fasting three days every month and that of Ramadan every year is a perpetual fasting.” (Sahih Muslim 1162a — Sahih)
Here the pattern is set out in full. Ramadan, kept every year, and three days in every month alongside it — together, in the Prophet’s ﷺ words, this is perpetual fasting. The one who fasts daily without rest gains nothing extra by the measure he gave; the one who keeps Ramadan and adds three days a month has, in his words, the perpetual fast itself.
The same narration continues with two more of the great monthly and yearly fasts, each stated with the Prophet’s ﷺ hope in Allah: his hope that fasting on the day of Arafah atones for the sins of the preceding and coming years, and that fasting on the day of Ashura atones for the sins of the preceding year. The three days of every month stand in this narration in noble company — among the fasts the Prophet ﷺ himself explained and praised.
4. Three Days Equal to the Whole Year
The same measure appears in the counsel the Prophet ﷺ gave to Abdullah bin Amr bin Al-As, who had taken to fasting every day of the year and praying every night. The Prophet ﷺ warned him about the cost of that excess:
“If you keep on doing this, your eyes will become weak and your body will get tired.” (Sahih al-Bukhari 1979 — Sahih)
Then he restated the principle about fasting without break:
“He who fasts all the year is as he who did not fast at all.” (Sahih al-Bukhari 1979 — Sahih)
And in place of the daily fast, he set before him the three days — with their worth stated plainly:
“The fasting of three days (a month) will be equal to the fasting of the whole year.” (Sahih al-Bukhari 1979 — Sahih)
Equal to the fasting of the whole year. This is the reward pattern the texts themselves state, and it is repeated across narrations: in Abu Dawud, the white days are “like keeping perpetual fast”; in Muslim, three days every month with Ramadan “is a perpetual fasting”; and here in Bukhari, three days a month “will be equal to the fasting of the whole year.”
Abdullah bin Amr answered that he had the power for more than this, and for the one who truly has that strength, the Prophet ﷺ pointed to the most that is praised:
“Then fast like the fasting of David who used to fast on alternate days and would never flee from the battle field, on meeting the enemy.” (Sahih al-Bukhari 1979 — Sahih)
Even here, the shape of the teaching is clear. There is a ceiling to what is recommended — the fast of David, alternate days — and there is a floor that already carries the full measure: three days every month. The white days are that floor, given fixed dates by the Prophet ﷺ himself.
5. Building the Monthly Rhythm
How does this fast fit into an ordinary life? Its beauty is in its regularity. Ramadan comes once a year, with its long nights of prayer and its month of discipline. The white days come twelve times a year — a small Ramadan-shaped pulse in every month, keeping the habit of fasting alive between one Ramadan and the next. Alongside other voluntary fasts in Islam, they are among the simplest to keep, because their dates are fixed and known in advance.
The dates to mark are the thirteenth, fourteenth and fifteenth of the Hijri month. Because these are lunar dates, they will not sit still on a solar calendar; a person follows the Islamic date of wherever he lives, the same reckoning by which his community begins and ends Ramadan. Many people find it helps to mark the three days at the start of each Islamic month, when the new moon has been sighted and the month’s dates are known.
It should be said clearly: this fast is voluntary. The Prophet ﷺ commanded it to his companions as a recommended practice, and the texts present it as a door to reward, not as an obligation like the fast of Ramadan. The one who keeps it gains what the narrations promise; the one who leaves it has not abandoned a duty. Its spirit is invitation, not burden — the same spirit in which the Prophet ﷺ turned Abdullah bin Amr away from fasting every single day and set three days a month before him instead.
The wider teaching of the narrations is about three days in every month, and the white days are the dates the Prophet ﷺ appointed for them. A person who is travelling, ill, or otherwise unable on the thirteenth to the fifteenth can still hold to the monthly rhythm the texts describe — three days within the month — and take up the white days again when the next moon reaches its fullness. The door does not close; it opens again every month.
6. Why Three Days Carry So Much
It is worth pausing over why three days should be spoken of in such large terms — a perpetual fast, the fasting of the whole year. The narrations state the equivalence without explaining its arithmetic, and we do not need to add explanations of our own. What the texts make plain is the comparison itself, and it is a comparison full of mercy.
Consider what the alternative looked like. A man came wanting to fast perpetually, and was told that the perpetual faster “neither fasted nor broke it.” Another fasted every day and prayed every night, and was told his eyes would weaken and his body would tire, and that fasting all the year is as fasting not at all. Against that background, the Prophet ﷺ set three days a month and declared them equal to the whole year. The reward of the maximum is attached to the measure almost anyone can carry.
This is the character of the virtues of fasting throughout the Sunnah: Allah’s generosity outruns our effort. The one who fasts Ramadan and then keeps three days in each month that follows has not fasted less, in the Prophet’s ﷺ accounting, than the one who never breaks his fast at all. And unlike the daily fast, this rhythm leaves the body its strength, the family its rights, and the worshipper his energy for everything else Allah loves — the very balance the Prophet ﷺ protected when he corrected those who wanted to do more.
There is one more quiet benefit in the fixed dates. A fast chosen at random is easily postponed; a fast appointed to the thirteenth, fourteenth and fifteenth arrives whether we feel ready or not, and the full moon itself becomes a reminder written in the sky. Month after month, the brightening nights announce that the white days are here. The one who answers that announcement, year after year, has built something the narrations describe in the largest terms available: a perpetual fast, sustained for a lifetime, three days at a time.
Other fasts fill out the year around this rhythm — the six fasts of Shawwal after Ramadan, the day of Arafah, the day of Ashura — but the white days are the steady heartbeat beneath them all, returning with every moon. Begin with the next full moon. Three days are coming, and the Prophet ﷺ has already told you what they are worth.
Frequently Asked Questions
Q1: What are the white days (Ayyam al-Beed)? They are the thirteenth, fourteenth and fifteenth days of every Islamic lunar month, named for their bright, full-moon nights. Qatadah Ibn Malhan al-Qaysi reported: “The Messenger of Allah (ﷺ) used to command us to fast the days of the white (nights): thirteenth, fourteenth and fifteenth of the month.” (Sunan Abu Dawud 2449 — Sahih)
Q2: What is the reward of fasting the white days? The Prophet ﷺ described the fast itself in the largest terms: “This is like keeping perpetual fast.” (Sunan Abu Dawud 2449 — Sahih) And he said: “The fasting of three days (a month) will be equal to the fasting of the whole year.” (Sahih al-Bukhari 1979 — Sahih)
Q3: Is fasting the white days obligatory? No. The only obligatory fast is Ramadan. The white days are a voluntary fast the Prophet ﷺ commanded as a recommended practice and praised highly, but the narrations present them as a door to reward — the Prophet ﷺ himself described the combined pattern as “Fasting three days every month and that of Ramadan every year is a perpetual fasting.” (Sahih Muslim 1162a — Sahih) Ramadan is the duty; the three days are the beloved addition.
Q4: Why not simply fast every day, if fasting is so rewarded? Because the Prophet ﷺ corrected that very ambition. Of the one who fasts perpetually he said: “He neither fasted nor broke it” (Sahih Muslim 1162a — Sahih), and he told Abdullah bin Amr, who fasted daily: “He who fasts all the year is as he who did not fast at all.” (Sahih al-Bukhari 1979 — Sahih) The most he praised for the strongest was the fast of David — alternate days — while three days a month already carry the year’s measure.
Q5: Which dates should I fast if I want to keep this practice? Fast the thirteenth, fourteenth and fifteenth of each Hijri month — the dates the Prophet ﷺ named when he commanded the fast of the white days. Follow the Islamic dates of your locality, the same reckoning used for Ramadan, and mark the three middle days when each new month begins.