Syedna Abu Hurairah, may Allah be pleased with him, narrates that a Bedouin brought a roasted rabbit to the service of the Messenger of Allah, peace and blessings be upon him, along with a sauce of mustard and raisins and some curry. He placed it before the Prophet, but the Messenger of Allah, peace and blessings be upon him, did not eat it himself; rather, he instructed his companions to eat. The Bedouin refrained from eating. The Messenger of Allah, peace and blessings be upon him, asked him: Why are you not eating? He replied: I fast three days every month (and today I am fasting). The Prophet, peace and blessings be upon him, said: If you wish to fast, then fast on the white days.

Ibn Hu Takiyah says that food was presented to Sayyiduna Umar (may Allah be pleased with him). He invited a man to eat, but he said: I am fasting. He (Umar) asked: On which days do you fast? If there was no fear of error, I would have told you a hadith of the Noble Prophet (peace and blessings be upon him), according to which a Bedouin once brought a rabbit to him. However, you should call Sayyiduna Ammar (may Allah be pleased with him). When he came, Sayyiduna Umar (may Allah be pleased with him) asked him: Were you present on the day when a Bedouin brought a rabbit to the service of the Noble Prophet (peace and blessings be upon him)? He replied: Yes. The Bedouin said: I saw that it bleeds. The Prophet (peace and blessings be upon him) said: You may eat it. The Bedouin said: I am fasting. The Prophet (peace and blessings be upon him) asked him: On which days of the month do you fast? He said: At the beginning and end of the month. The Prophet (peace and blessings be upon him) said: If you wish to fast, then fast on the 13th, 14th, and 15th of the lunar month.

It is narrated from Sayyiduna Minhal (may Allah be pleased with him) that the Messenger of Allah (peace and blessings be upon him and his family) commanded us to fast on the White Days; these are equal to fasting for a whole month.

(Second chain) He says: The Messenger of Allah, peace and blessings be upon him, commanded us to fast on the white days, that is, the 13th, 14th, and 15th of the lunar month, and said: These are equal to fasting for the whole year.

It is narrated from Sayyiduna Abu Dharr (may Allah be pleased with him) that the Messenger of Allah (peace and blessings be upon him) said: Whoever among you wishes to fast three days in a month, let him fast on the three days of Ayyam al-Beedh (the white days).