What is the status of this hadith:
Anas رضي الله عنه narrates that the Prophet ﷺ said, “In Rajab, there is a night on which a hundred rewards are written for the one who worships in it. That is when three days remain of Rajab (i.e. the 27th night). Whosoever performs twelve rakats on it (this night), recites the Fatihah of the Book and a Surah of the Quran in every two rakat, makes salam on the end of them, then says, “Subhannallah, walhumdulillah, wa Laa ilaaha illallah wallahu akbar’ a hundred times, sends salutation on the Prophet ﷺ a hundred times, supplicates for himself whatever he wishes of his worldly affairs and the Hereafter and fast in the morning, then Allah will accept all his supplications unless he asks for a sin.”
Answer: حامدا ومصليا ومسلما
This narration has, not one, but two unscrupulous narrators in it, which renders it totally unreliable to practice on or even quote as a matter of virtue.
Imam Baihaqi رحمه الله collected this narration in his ‘Shuabul Iman’ to point out its unreliability. He starts off by saying, “And from amongst the manakir (strange and extremely weak or fabricated) narrations mentioned on this issue is what Abu Abdillah Al-Hafiz narrated to us … that Khalid ibn Al-Haiyyaaj narrated to us from his father … that Salman Farsi رضي الله عنه said that the Messenger of Allah ﷺ said, ‘In Rajab there is a day and night, that whoever fast on that day and stand on that night (in salah) is like the one who fasted a hundred years of time and stood for a hundred years (in salah). It is three nights reaming of Rajab (27th) and on it Allah sent Muhammad.’”
Concerning this narration Hafiz Ibn Hajr Asqalani رحمه الله said in ‘Tabyinul ‘Ajab’, “This hadith is munkar to the limit. Haiyyaaj, who is Ibn Bistaam Al-Harawi has narrated from a group of tabieen. Ibn Maeen رحمه الله has graded him weak. Abu Dawud رحمه الله said, ‘They (the muhaddithun) have abandoned him.’ Salih ibn Muhammad Al-Hafiz رحمه الله said, ‘Al-Haiyyaj is mukarul hadith, only two or three of his hadiths can be written for further research purposes. I did not know all this about him until I came to Haraah and I saw with him many manakir ahadith.’ Al-Hakim Abu Abdillah رحمه الله said, ‘These ahadith, which Salih رحمه الله saw from the ahadith of Al-Haiyyaaj, the sin in them is on his son Khalid.’” After understanding the extreme weakness of this narration, we would fully appreciate Imam Baihaqi’s statement concerning the narration cited in the question.
After this narration of al-Haiyyaaj, Imam Baihaqi رحمه الله says, “And this has been narrated with an even weaker chain than this…” Then he mentions the narration cited in the question.
Reasons for the Unreliability of the Narration in Question:
Allamah Ibn Arraq رحمه الله said in ‘Tanzeehus Shariah’, “Baihaqi رحمه الله narrated it and in it(‘s chain) are two (narrators) charged with lying, Muhammad ibnul Fadhl ibn ‘Atiyah and Abaan ibn Abi ‘Ayyaash.”
Mulla Ali Qaari رحمه الله also deemed it unreliable in his ‘Al-Adab fir Rajab’.
It is sad to see that around a thousand years ago Imam Baihaqi رحمه الله collected this unreliable narration to warn us against it and people are forwarding it on social media as thought it is authentic. May Allah protect us from knowledge that will not benefit.
And Allah Ta’ala knows best.
 Vol.5 Pg.346 #3531
 Vol.2 Pg.90
 See Tabyinul ‘Ajab Pg.43-44 He graded its chain dark and unknown.
 Al-Aathaarul Marfoo’ah Pg.61-62