Shaykh Ibn Baz (may Allah have mercy on him) said in Hukm al-Ihtifal bi Laylat al-Nisf min Sha’ban (Ruling on celebrating the fifteenth of Sha’ban):
“Celebrating the night of the fifteenth of Sha’ban (Laylat al-Nisf min Sha’ban) by praying etc, or singling out this day for fasting, is a reprehensible bid’ah (innovation) according to the majority of scholars, and there is no basis for this in Shari’ah.”
And he (may Allah have mercy on him) said:
“There is no sahih hadith concerning the night of the fifteenth of Sha’ban (Laylat al-Nisf min Sha’ban). All the ahadith that have been narrated concerning that are mawdu’ (fabricated) and da’if (weak), and have no basis. There is nothing special about this night, and no recitation of Quran or prayer, whether alone or in congregation, is specified for this night. What some of the scholars have said about it being special is a weak opinion. It is not permissible to single it out for any special actions. This is the correct view. And Allah is the Source of strength.” (Fatawa Islamiyyah, 4/511)
Source: https://islamqa.info/en/answers/49675/is-fasting-on-the-15th-of-shaban-recommended
