The Messenger of Allah ﷺ used to fast three days at the beginning of every month.In another narration, "I rarely saw the Messenger of Allah ﷺ not fasting on Friday."
كان رسول الله ﷺ يصوم من غرة كل شهر ثلاثة أيام. وفي رواية: قلما رأيت رسول الله ﷺ يفطر يوم الجمعة.
Abu Dawud (2400), Tirmidhi (742), and Ibn Majah (1725) all narrated it through Shayban, from Asim, from Zirr, from Abdullah bin Masud, who related it. Tirmidhi said, "The hadith of Abdullah is hasan gharib. Some of the people of knowledge recommended fasting on Friday. What is disliked is fasting on Friday alone, without fasting the day before or after it. Shubah narrated this hadith from Asim without raising it to the Prophet. On this subject there are also narrations from Ibn Umar and Abu Hurairah." End of quote. Ibn Khuzayma (2129) and Ibn Hibban (3641) also graded it sahih, narrating it in their two Sahihs by this route.I say, its chain is hasan, because of Asim, who is Ibn Abu Najud, and he is hasan al-hadith. As for the disagreement over whether it is raised to the Prophet or stopped at the companion, Hafiz Daraqutni said in Ilal (5/60), "Raising it to the Prophet is sahih." As for the meaning of the hadith, it is as Tirmidhi said, that the Prophet used to fast on Thursday and Friday, while singling out Friday alone for fasting has been established as prohibited.As for what was narrated from Junada Azdi, that eight men came to the Messenger of Allah ﷺ, and he was the eighth of them. The Messenger of Allah ﷺ brought food near them on a Friday and said, "Eat." They said, "We are fasting." He said, "Did you fast yesterday?" They said, "No." He said, "Will you fast tomorrow?" They said, "No." He said, "Then break your fast." This is daif. It was narrated by Nasai in Kubra (2786), Ahmad (4/24009), Tabarani in Kabir (2173), and Hakim (3/60), all through routes from Yazid bin Abu Habib, from Marthad bin Abdullah Yazani, Abu Khayr, from Huzaifa Bariqi, from Junada Azdi, who related it, the wording being Nasai's. Some added to the text, "So we ate with the Messenger of Allah ﷺ. Then when he went out and sat on the pulpit, with the people watching, he showed them that he was not fasting on Friday." Hakim said, "It is sahih according to the criterion of Muslim." But the correct view is that it is not according to the criterion of Muslim, for Huzaifa Bariqi, also said to be Azdi, was only narrated from by Nasai, and no one but Marthad bin Abdullah narrated from him. That is why Dhahabi said of him, "Unknown." And Hafiz said, "Acceptable." As for his statement in Fath al-Bari (4/234) that Nasai narrated it with a sahih chain, it appears that he, may Allah have mercy on him, erred in this.Likewise, what is narrated from Ibn Abbas as a raised hadith, "Do not fast on Friday alone," is not sound. Ahmad narrated it (2615) from Itaab bin Ziyad, who said, Abdullah informed us, who said, Husayn bin Abdullah bin Ubaydullah bin Abbas informed us, from Ikrima, from Ibn Abbas, who related it. But Husayn bin Abdullah bin Ubaydullah bin Abbas bin Abdul-Muttalib Hashimi is daif.Likewise, what is narrated from Abu Hurairah as a raised hadith, "Friday is a day of festival, so do not make your day of festival a day of your fasting, unless you fast the day before or after it," is not sound. Imam Ahmad narrated it (8025) from Abdul-Rahman, that is Ibn Mahdi, from Muawiya, meaning Ibn Salih, from Abu Bishr, from Amir bin Ludayn Ashari, from Abu Hurairah, who related it. Hakim narrated it by this same route (1/437) and said, "This is a hadith sahih in its chain, though the two of them (Bukhari and Muslim) did not narrate it, except that I have not been able to determine the name of this Abu Bishr, and he is neither Bayan bin Bishr nor Jafar bin Abu Wahshiya." Dhahabi said in his summary, "He is unknown." And Hafiz said of him, "Acceptable, if he is the muezzin of Damascus, but if Abu Bishr is the companion of Abu Zahiriya, then he is daif." Ibn Khuzayma said in his Sahih (2162), after narrating it through the route of Ibn Mahdi, "This Abu Bishr is Syrian, and is not the Abu Bishr Jafar bin Abu Wahshiya, the companion of Shubah and Hushaym."