Hadith on the virtue of this night:
Muʿaẓ ibn Jabal narrated that the Prophet ﷺ said:
“Allah pays special attention to his entire creation on the fifteenth night of Shaʿban and forgives all of them except one who ascribes partners to Him and one who harbours enmity in his heart.” [Al-Muʿjam al-Kabīr vol.20 pg.108-109]
— Ibn Ḥibbān has classified this narration as Ṣaḥīḥ (authentic) [Ṣaḥīḥ ibn Ḥibbān Vol.12 pg.482; Ḥadīth: 5665]
— Ḥāfiẓ Al-Haythamī has mentioned that all the narrators of this ḥadīth are reliable. [Majmaʿ al-Zawā’id Vol. 8 pg. 65]
ʿAbdullah ibn ʿUmar related that the Prophet ﷺ said:
“There are five nights on which duʿa is not turned back: Friday eve, on the eve of Rajab, the 15th night of Sha‘ban, Laylat al-Qadr, and on the eve of the two Eids.” [Muṣannaf ʿAbd ar-Razzāq, Ḥadīth 7927; authenticity unverified]
Statements of the Scholars:
Imam ash-Shafiʿi states in al-Umm:
“It has reached us that it is said that there are five nights when the duʿas are accepted; the night of Friday, the night of Eid al-Aḍḥa, the night of Eid al- Fiṭr, the first night of Rajab and the 15th of Sha‘ban.”
Shaykh ʿAbd al-Qadir al-Jilani states in Ghunya al-Ṭālibīn:
“Malik ibn Anas reports from ʿUrwah, from ʿAisha (may Allah be pleased with her) who said she heard the Prophet ﷺ state that: ‘There are four nights in which the gates of righteousness are opened; the night of Eid al-Aḍḥa, the night of Eid al-Fiṭr, the night of ʿArafa (9th Dhu ʾl-Hajj) and 15th of Shaʿban.'” [pg. 448]
Al-Ajhuri al-Maliki records in Ḥusnul Bayān:
“‘Aṭā ibn Yasār—the great Tabiʿi of Madinah—said: ‘After Laylat al-Qadr, there is no other night in the year that is more virtuous than the middle (15th) night of Shaʿban.’” [pg.11]
Ibn al-Ḥajj states in al-Madkhal:
“This night has great virtue and abundant good.” He further says, “The salaf (pious predecessors) would sanctify this night and prepare themselves for it in advance.” [1/299]
Ibn Qudamah al-Maqdisi states in Mukhtaṣar Minhāj al-Qāṣidīn:
“The most virtuous nights, that the devout servant of Allah should observe Qiyam al-Layl therein, are:
—The odd nights from the last ten nights of Ramaḍan,
—1st and 10th of Muharram,
—1st and 15th of Rajab,
—15th of Sha’ban…”
Ibn Rajab al-Ḥanbalī states in Laṭāʾif al-Maʿārif:
“…There is nothing established from the Messenger of Allah ﷺ nor from his companions with regard to spending the 15th night of Shaʿban in worship. But it is established that a group of Tābiʿūn —who were senior jurists of Shām—used to spend this night in worship.” He further says, “…It is thus the duty of every believer to free himself on the night for the remembrance of Allah and supplicating to Him for the forgiveness of sins, concealment of faults, and removal of hardships. And he should precede all this with repentance because Allah Almighty turns to the one who repents to Him on this night.” [pg. 264-265]
All of the above sufficiently confirms the significance of the 15th night of Sha’ban. As for a list of optional acts that can be performed on this night, see:
Optional Acts for the Night of Emancipation—15th of Sha’ban
May Allah ﷻ guide us all, and may He ﷻ allow us to maximise our benefit from the auspiciousness of this night.