This excerpt is taken from Kitab al-Sawm, compiled by Sheikh Ghulam Mustafa Zaheer Amanpuri, may Allah preserve him.
Question:
What is meant by Ayyam al-Beed?
Answer:
Ayyam al-Beed refers to the 13th, 14th, and 15th days of the lunar month. Since the moon is brightest on these three nights, they are called Beed, meaning bright.
Question:
What is the virtue of fasting on Ayyam al-Beed?
Answer:
Fasting on the days of Ayyam al-Beed (the 13th, 14th, and 15th of the lunar month) is prescribed and recommended. There are authentic hadiths as evidence for this. These three fasts are equivalent to fasting the entire month; if these three fasts are observed every month, the reward of fasting the whole year will be attained. Muslims of every era have practiced this.
❀ The Noble Prophet Muhammad ﷺ said to Sayyiduna Abu Dharr رضي الله عنه:
إذا صمت من الشهر ثلاثة أيام فصم ثلاث عشرة وأربع عشرة وخمس عشرة
"When you fast three days every month, fast on the 13th, 14th, and 15th (Ayyam al-Beed) of the lunar month."
Reference: (Sunan an-Nasa'i: 2424, Sunan at-Tirmidhi: 761, and its chain is Hasan)
Imam Tirmidhi رحمه الله said this hadith is Hasan, and Imam Ibn Khuzaymah رحمه الله
Reference: (2128)
and Imam Ibn Hibban رحمه الله
Reference: (3656)
declared it Sahih.The Noble Prophet Muhammad ﷺ said to Sayyiduna Abdullah bin Amr رضي الله عنهما:
إن بحسبك أن تصوم كل شهر ثلاثة أيام فإن لك بكل حسنة عشر أمثالها فإن ذلك صيام الدهر كله
"It is sufficient for you to fast three days every month, and you will receive ten times the reward for every good deed, and thus you will have the reward equivalent to fasting the entire year."
Reference: (Sahih al-Bukhari: 1975, Sahih Muslim: 1159)
❀ Yazid bin Abdullah bin Shukheer رحمه الله narrates that he heard the Messenger of Allah ﷺ say:
صوم شهر الصبر وصوم ثلاثة أيام من كل شهر يذهبن وحر الصدر
"Fasting in the month of Ramadan and fasting three days every month removes hatred from the heart."
Reference: (Musnad al-Imam Ahmad: 5/263, Sunan Abi Dawood: 2999, Sunan an-Nasa'i: 4151, and its chain is Sahih)
Imam Ibn Hibban رحمه الله
Reference: (6557)
and Imam Ibn al-Jarood رحمه الله
Reference: (1099)
declared this hadith Sahih.❀ Musa bin Salamah رحمه الله narrates:
سألت ابن عباس عن صيام ثلاثة أيام البيض فقال كان عمر يصومهن
"I asked Sayyiduna Abdullah bin Abbas رضي الله عنهما about the three fasts of Ayyam al-Beed, and he said: Sayyiduna Umar bin Khattab رضي الله عنه used to fast these days."
Reference: (Musnad al-Harith [Bughyat al-Bahith]: 340, and its chain is Sahih)