Musa bin Talhah narrated: Sayyiduna Umar (may Allah be pleased with him) asked Sayyiduna Abu Dharr al-Ghifari (may Allah be pleased with him), Sayyiduna Ammar (may Allah be pleased with him) and Sayyiduna Abu al-Darda' (may Allah be pleased with him): "Do you remember the day when we were with the Prophet (peace and blessings be upon him) at such-and-such a place, and a bedouin came to him with a rabbit which had blood on it (i.e. it was a female rabbit that menstruated), and the Prophet (peace and blessings be upon him) commanded us to eat it, and that bedouin did not eat it?" They replied: "Yes. The Prophet (peace and blessings be upon him) said to him: 'Come closer and eat.' He said: 'I am fasting; I fast three days every month, at the beginning of the month or at its end, as is easy for me.'" Sayyiduna Umar (may Allah be pleased with him) said: "Do you know what the Prophet (peace and blessings be upon him) commanded that man?" They replied: "The Prophet (peace and blessings be upon him) commanded him to fast on the thirteenth, fourteenth and fifteenth." He said: "That is how the Prophet (peace and blessings be upon him) said it." (Allamah al-Haythami says:) I say: The report narrated from Sayyiduna Abu Dharr al-Ghifari (may Allah be pleased with him) alone was recorded by Imam al-Tirmidhi in abridged form.
Imam al-Tabarani recorded it in al-Mu'jam al-Kabir. Its chain contains a narrator, Hakim bin Jubayr, about whom much has been said. Abu Zur'ah said: His position is truthfulness, if Allah wills.
Hadith Referenceمجمع الزوائد ومنبع الفوائد / كتاب الصيام / 5182