All Praise belongs to Allah the Lord of the worlds and may peace and blessings be upon his last and final messenger, Muhammad.
Imam al-Allamah al-Hattab al-Maliki says in his commentary on. "The Mukhtasar of Khalil." (3/318), "from amongst the days which it is recommended to fast are other days which the author (Imam Khalil ibn Ishaq) did not mention, amongst them the 3rd of Muharram, the 20th of Rajab, the 15th of Sha'ban and the 25th of Dhul-Qi'dah."
and he also says, "As for the 15th of Sha'ban, Ibn Arafah when he mentioned in his work what is transmitted regarding the excellence of fasting in Sha'ban he mentioned it is especially recommended to fast the 15th of Sha'ban." (Ibid)
The Shaykh of Azhar, Imam al-Allamah al-'Iliyish in his commentary on, "The Mukhtasar of Khalil.", "And it is disliked to gather for dua or remembrance, prayer, or its like the night of Arafah, the 15th night of Sha'ban, and the 27th night of Rajab and Ramadan in the Mosques and besides them if one intends to be like the Pilgrims or that doing all this is a sunnah and if one does not have these intentions it is recommended to gather for remembrance, prayer and the like on all of these nights."
Allamah al-Nafarawi says in his commentary, "Al-Fawakih al-Dawani." (2,652) on, "The Epistle of Ibn Abi Zayd al-Qayrawani." the Prophet's saying, 'Whoever spends the night of Eid, and the 15th Night of Sha'ban his heart will not die the day hearts die." what is meant by his heart not dying is that his heart will not be scared upon death nor on the day of judgement, and it is said it will not die with the love of this world, and staying up takes place by divine remembrance and prayer for most of the night."
Allamah al-Khirshi in his commentary (102-2/101) on, "The Mukhtasar of Imam Khalil." says, "Whoever stays up at night in worship on the night of Eid and the 15th of Sha'ban his heart will not die the day hearts will perish, what is meant by his heart not dying is that he will not be scared upon his death nor shall he be scared on the day of judgement, what is meant by, "the day." the entire period of his death, time in his grave, and the day of judgement, and one is considered to have stayed up the night in worship by spending most of the night upon the clear view with Salah, remembrance, and amongst the recommend actions upon the mashur opinion is to perform ghusl."