Praise be to Allah.
This is mentioned in some ahaadeeth, but there is some scholarly difference of opinion as to the soundness of those ahaadeeth. There is no saheeh hadeeth concerning the virtue of the night of the fifteenth of Sha’baan.
It was narrated from Abu Moosa al-Ash’ari that the Messenger of Allah (peace and blessings of Allah be upon him) said: “Allah looks down on the night of the fifteenth of Sha’baan and forgives all his creation except a mushrik or one who harbours hatred against the Muslims.” [Narrated by Ibn Maajah, 1390.]
The “one who harbours hatred against the Muslims” means one who has enmity towards a Muslim brother.
In al-Zawaa’id it says: “Its isnaad is da’eef, because ‘Abd-Allaah ibn Lahee’ah is da’eef (weak) and al-Waleed ibn Muslim is mudallis.”
There is also some idtiraab (weakness) in the hadeeth, as stated by al-Daaraqutni in al-‘Ilal, 6/50, 51. He said: “This hadeeth is not proven.”
It was narrated from Mu’aadh ibn Jabal, ‘Aa’ishah, Abu Hurayrah, Abu Tha’labah al-Khushani and others, but the isnaads are not free of some weakness, and some of them are very weak.
Ibn Rajab al-Hanbali said:
“Concerning the virtue of the night of the fifteenth of Sha’baan there are numerous ahaadeeth, concerning which the scholars differed, but most of them classed them as da’eef, and Ibn Hibbaan classed some of them as saheeh.” [Lataa’if al-Ma’aazif, 261.]
Allah’s descending to the first heaven does not only happen on the night of the fifteenth of Sha’baan, rather it is proven in al-Saheehayn and elsewhere that Allah descends to the first heaven every night, in the last third of the night. The night of the fifteenth of Sha’baan is included in this general meaning.
Hence, when ‘Abd-Allaah ibn al-Mubaarak was asked about the descent of Allah on the night of the fifteenth of Sha’baan, he said to the one who asked him: “O weak one! The night of the fifteenth?! He descends every night!” [Narrated by Abu ‘Uthmaan al-Saabooni in I’tiqaad Ahl al-Sunnah, no. 92.]
Al-‘Aqeeli (may Allah have mercy on him) said:
“With regard to Allah’s descending on the night of the fifteenth of Sha’baan there are ahaadeeth which are weak, but the reports that He descends every night are proven and saheeh, so the night of the fifteenth of Sha’baan is included in that, in sha Allah.” [Al-Du’afa’, 3/29.]
There is no saheeh marfoo’ report that speaks of the virtue of the middle of Sha’baan that may be followed, not even in the chapters on al-Fadaa’il (chapters on virtues in books of hadeeth etc.). Some maqtoo’ reports (reports whose isnaads do not go back further than the Taabi’een) have been narrated from some of the Taabi’een, and there are some ahaadeeth, the best of which are mawdoo’ (fabricated) or da’eef jiddan (very weak).
These reports became very well known in some countries which were overwhelmed by ignorance; these reports suggest that people’s lifespans are written on that day or that it is decided on that day who is to die in the coming year. On this basis, it is not prescribed to spend this night in prayer or to fast on this day, or to single it out for certain acts of worship. One should not be deceived by the large numbers of ignorant people who do these things. And Allah knows best. [Shaykh Ibn Jibreen.]
If a person wants to pray qiyaam on this night as he does on other nights – without doing anything extra or singling this night out for anything – then that is OK.
The same applies if he fasts the day of the fifteenth of Sha’baan because it happens to be one of the ayyaam al-beed, along with the fourteenth and thirteenth of the month, or because it happens to be a Monday or Thursday. If the fifteenth (of Sha’baan) coincides with a Monday or Thursday, there is nothing wrong with that (fasting on that day), so long as he is not seeking extra reward that has not been proven (in the saheeh texts).
And Allah knows best.