The fast of the 15th of Sha’ban exclusively, sunnah ?

The following hadith is often quoted to back the fast of the 15th of Sha’ban :

Narrated by Sayyiduna ‘Ali (RA), the Prophet [saws] said : When the Middle Night of Shabaan arrives, you should stand (Praying) in the night and should fast in the day following it

This Hadith is recorded by Ibn Majah in his Sunan, one of the famous six books of Hadith, and also by Baihaqi in his famous book Shu’ab-al-‘iman’.  In its chain there is Abu Bakr ibn Abi Saburah who is considered as a weak narrator, so this hadith cannot be relied upon in the matter of the injunctions of Shariah. Thus, the fast of the 15th of Shabaan cannot be termed as Sunnah or Mustahab in the strict sense of the term.

(((As for the virtues of the 15th night, its authenticity is well-known and not the subject here. Proofs can be found here for example.)))

The following muhaddithun have severely criticised Abu Bakr ibn Abi Saburah :

Al-Boukhâri
Ali ibnul Madini
Abu Bakr Al Bazzar
The two sons of Imam Ahmad
Ibnu ‘Adi
Ibnu Hibban
Al-Hakim
An-Nassa’i
Ibnu Ma’in
Al-Haythami

Consequently the following ‘Ulama have criticised the aforementioned hadith :

Imam Badruddin Al-‘Ayni
Al-‘Iraqi
Ibn Rajab Al-Hanbali
Ibnul Jawzi
Ash-Shawkani

May Allah have mercy upon them all.

Can I use very weak hadith ?

To sum up : To fast the 15th day of Sha’ban exclusively is not sunnah nor mustahhab, but you can perfectly fast the 2nd, 4th, 7th, 10th, 13th, 14th and 15th days (Ayyam al-bîd) or even the first half of the month of Sha’ban, if you do care about Sunnah.

Jazakumullahu Kheyran, and requests for du’a.