In the first place, we would like to stress that there is nothing authentic that has been established on the authority of the Prophet (peace and blessings be upon him), that he held night vigil prayer and fasted during the day of the 15th of Sha`ban.

Responding to the question, Dr. Sano Koutoub Moustapha, professor of jurisprudence and its principles at the International Islamic University, Malaysia, states the following:

Thank you for your question.

It is true that there is no authentic hadith which calls upon Muslims to perform special prayers, fasting or special worship in the month of Sha`ban. Having said this, I shall mention that there is an authentic hadith which states that the Prophet (peace and blessings be upon him) used to fast most of the month of Sha`ban and Usamah ibn Zaid asked him why he fasts most of this month. He replied by saying, “It is a month that the people forget about it, it is between Rajab and Ramadan, it is a month in which all deeds are brought to the attention of the Almighty. Therefore, I would like my deeds to be presented to Allah while I am fasting.” (Reported by Al-Bukhari)

According to this hadith, it is strongly recommended to fast in this month as much as we can, while bearing in mind that it is not allowed to fast the whole month. Furthermore, it is strongly recommended to keep imploring the Almighty to bestow upon you good health and enable you to fast the holy month of Ramadan.

Moreover, Sheikh Ahmad Kutty, a senior lecturer and an Islamic scholar at the Islamic Institute of Toronto, Ontario, Canada, adds:

There are no prescribed rituals of worship to be performed on the 15th of Sha`ban. If there had been any such rituals to be performed, then it would have been stated clearly in the authentic traditions.

Having said this, we cannot stop people from performing nawafil any time; for nawafil are simply optional prayers; no one can stop anyone from performing them any time except those times when prayers are forbidden.