There is no authentic hadith reported about the 15th night of Sha`ban. The hadiths reported about that night are classified by some scholars as hasan (hadith hasan is a hadith whose authenticity is not as well-established as that of Sahih, but sufficient for use). Some other scholars have refused these hadiths, considering them unauthentic.
The hadiths considered as hasan are to the effect that it is recommendable to supplicate Almighty Allah during this night and ask Him for forgiveness. But there is no specific supplication reported to be said in this night. Hence, the supplications that some print and distribute among people in some Muslim countries as being recommendable on this night is not correct and has no basis in the sharia.

To shed more light on this, Sheikh `Atiyyah Saqr, former head of Al-Azhar Fatwa Committee, states:

There are three points to be discussed in handling the question in hand: The first point has to do with whether the 15th night of Sha`ban has a special significance; the second concentrates on whether the Prophet (peace and blessings be upon him) celebrated this night; the third tackles whether there are special acts to celebrate this night or special supplications to invoke Almighty Allah with.

First, there are some hadiths indicating that the 15th night of Sha`ban is significant. Some scholars classified some of these hadiths as authentic. On the other hand, some other scholars considered them as da`if  (weak), yet they hold that these hadiths may be acted upon by him who seeks to get closer to Almighty Allah with additional acts of worship.

Of these hadiths is one that is reported by Imam Ahmad and At-Tabarani to the effect that the Prophet (peace and blessings be upon him) said, “Almighty Allah descends to the lowest Heaven on the 15th night of Sha`ban and forgives such number of people that is more than the number of the hairs of the sheep of Banu Kalb (a tribe that has a great number of sheep).” But At-Tirmidhi said that Imam Al-Bukhari classified this hadith as weak.

It was also reported on this subject that `A’ishah, Mother of the Believers, said: The Prophet (peace and blessings be upon him) offered the night vigil Prayer some night, and while he was praying, he prostrated so long that I thought he had passed away, but he lifted his head and finished the Prayer. Then he (peace and blessings be upon him) said, “O `A’ishah (or O Humaira [as he would call her]), have you thought that the Prophet (peace and blessings be upon him) would not give you your right?” I said, “No, by Allah, Allah’s Messenger. But when you stayed prostrating so long, I thought you had passed away.” The Prophet (peace and blessings be upon him) then said, “Do you know what night this is?” I said, “Allah and His Messenger know best.” He (peace and blessings be upon him) said, “This is the 15th night of Sha`ban. Almighty Allah turns towards His servants on the 15th of Sha`ban and forgives those who ask for His forgiveness, grants mercy to those who ask for it, and delays (punishing or bringing to account) the evil people.” (Al-Baihaqi)

This hadith was reported by Al-Baihaqi on the authority of Al-`Ala’ ibn Al-Harith, one of the successors (At-Tabi`un), which means that this hadith is mursal (reported by a successor immediately on the authenticity of Mother of the Believers or the Prophet himself without having a Companion in between in the chain of reporters). Al-Baihaqi said this is a good mursalhadith.

Ibn Majah also reported with a weak chain of reporters on the authority of `Ali (may Allah be pleased with him) that the Prophet (peace and blessings be upon him) said, “When the 15th night of Sha`ban comes, observe night vigil Prayer during it and fast the following day, for Almighty Allah descends after sunset on that night to the lowest Heaven and says, ‘Is there anyone who seeks My forgiveness and I forgive him (or her)? Is there anyone who is in need to ask Me and I provide for his (or her) needs. Is there anyone who is in pain and seeks My help and I help him (or her)? Is there…? Is there…?’ until the time of dawn.”
Based on these hadiths and others, it may be said that the 15th night of Sha`ban has a special significance. In fact, there is no religious text that stands against this, especially that the merit of the month of Sha`ban as a whole is established.

Usamah ibn Zayd (may Allah be pleased with both of them) was reported to have said that he asked the Prophet (peace and blessings be upon him), “I have not seen you observe additional fast during any month [other than Ramadan] as you do in Sha`ban?” He (peace and blessings be upon him) replied, “This is a month that people usually forget about between Rajab and Ramadan, and it is a month in which people’s deeds are presented to Allah, so I like that my deeds are presented while I am fasting.” (An-Nasa’i)

The second point to be dealt with is whether he (peace and blessings be upon him) celebrated this night. In this regard, it was established that the way he (peace and blessings be upon him) celebrated this month was by fasting during it.

As to whether the Prophet (peace and blessings be upon him) observed night vigil Prayer on this night, he (peace and blessings be upon him) would regularly observe night vigil Prayers during nights, and observing night vigil Prayer on this night is like doing so during the other nights. Hence, observing night vigil Prayer on the 15th of Sha`ban may be recommended, as supported by the hadiths reported above, especially the one in which he (peace and blessings be upon him) advised his Companions to observe night vigil Prayer on it and the one reported by `A’ishah to the effect that he (peace and blessings be upon him) observed night vigil Prayer on it. Though these hadiths are weak, they are dependable in seeking to get close to Almighty Allah with additional acts of worship.

This indicates that he (peace and blessings be upon him) celebrated that night in this way individually, not in congregation with his Companions. Neither he (peace and blessings be upon him) nor his Companions (may Allah be pleased with all of them) would offer celebrations on this night as people do nowadays.

The celebrations seen nowadays on this night began in the era of the followers of the righteous predecessors. According to Al-Mawahib Al-Ladduniyyah, vol. 2, by Al-Qastalani, the successors in the Levant, such as Khalid ibn Mi`dan and Makhul would observe further additional acts of worship on the 15th night of Sha`ban, and, hence, people followed them in assuming special significance to this night. It was even said that those followers would follow Israelite reports concerning the merit of this night.

When this was circulated in the Muslim world, controversy aroused concerning the correctness of such a deed. The majority of scholars in Makkah and Madinah then, including `Ata’, Ibn Abi Mulkyah, the followers of Malik, and others, disapproved of such a deed, considering it an innovation in religion.

Al-Qastalani then said that there were two different views among the scholars of the Levant regarding how to celebrate this night. The first opinion says that it is recommendable that people congregate in mosques to offer night vigil Prayer as a way of celebrating it. Khalid ibn Mi`dan, Luqman ibn `Amir, and others would dress in their best clothes, wear kohl and perfume, and offer night vigil Prayer on this night.

Ishaq ibn Rahawiyah was reported by Harb Al-Karamani to have approved of this opinion saying that observing night vigil Prayer in congregations in mosques on this night is not an innovation.

The second view is to the effect that it is reprehensible that people congregate in mosques especially on this night to offer night vigil Prayer and supplicate in groups, but it is not reprehensible that one offers night vigil Prayer on this night individually. This opinion was held by Al-Awza`i, the Imam of the scholars of the Levant.

Al-Qastalani also tackled in Al-Mawahib Al-Ludaniyah the opinions of Imam Ahmad on the issue. According to him, there is no specific view reported to have been held by Imam Ahmad with regard to celebrating the 15th night of Sha`ban. His opinions in this regard are concluded from the views attributed to him concerning observing night vigil Prayers on the nights of the two `Eids. He had two points of views in this regard. He was reported to have said that observing night vigil Prayers on the nights of the two `Eids is not recommendable, for neither the Prophet (peace and blessings be upon him) nor his Companions would do so. However, he was also reported to have considered observing night vigil Prayers on these nights as recommendable, for `Abdur-Rahman ibn Zaid ibn Al-Aswad, a successor, would do so. These views may apply also to the case of the 15th night of Sha`ban.

To sum up what Al-Qastalani said on the issue, scholars have differed concerning observing night vigil Prayer on the 15th night of Sha`ban in congregations in mosques: some are for and some are against.

Hence, I see that since the issue is controversial, one may follow one of these opinions without showing extreme opposition against the other view. However, some contemporary scholars see that the reason for celebrating the 15th night of Sha`ban is mainly to commemorate the change of the direction of prayer from Jerusalem to Makkah, not any other reason. But the date of this change is not certain to be Sha`ban 15; the exact date of this event is also controversial among scholars. Anyway, commemorating events also has the legal rulings pertaining to it. I see that there is nothing wrong in commemorating this special event so long as there is nothing wrong committed in this regard and it is done for Almighty Allah’s sake.
the third point to be discussed here has to do with whether there are special supplications to be offered on this night and whether it is lawful to observe the night vigil Prayer then with the intention of concentrating on asking Almighty Allah to prolong one’s life and enrich one.

Offering optional Prayer with the intention of doing so as a means of getting closer to Almighty Allah is wholeheartedly recommendable. Furthermore, it is an act of sunnah to offer supererogatory Prayers in the time between Maghrib and `Isha’ Prayers and after the `Isha’ Prayer. But offering an optional Prayer so that Almighty Allah may prolong one’s life and enrich one has no basis in Shari`ah.

An-Nawawi said in his book Al-Majmu`: Ar-Ragha’ib Prayer, i.e., a 12-rak`ah Prayer between Maghrib and `Isha’ Prayers said to be recommendable in the first Friday of Rajab, and the 100-rak`ah Prayer said to be recommendable on the 15th night of Sha`ban are innovations in religion. Their being mentioned in eminent books like Qut Al-Qulubby Abu Talib Al-Makki and Ihya’ `Ulum Ad-Din by Imam Al-Ghazali should not make people believe that they are really recommendable acts of sunnah. Besides, the hadith mentioning these Prayers is not an authentic one, and the eminent scholars who thought that these Prayers are recommendable are wrong in their judgment in this respect.

Moreover, Sheikh Abu Muhammad Abdur-Rahman ibn Isma`il Al-Maqdisi wrote a great book specially to refute these two hadiths (Al-Azhar Magazine, vol. 2, p. 515).

Concerning offering special supplications on this night, there is also no authentic hadith reported in this respect. What is reported in this regard is `A’ishah’s saying: “I heard him—the Prophet (peace and blessings be upon him)—saying: ‘O Allah! I seek refuge in Your pardon against Your punishment, I seek refuge in Your pleasure against Your displeasure, and I seek refuge in You against You (Your wrath). Whatever great praises I attribute to You, they cannot stand comparison with the praises You, Almighty, has attributed to Yourself’” (Al-Bayhaqi on the authority of Al-`Ala’ ibn Al-Harith).

The supplication circulated nowadays as recommendable to be offered on this night is: “O Allah, Who has favors unto His servants and no one is to have favor unto Him! O Allah, the Owner of majesty and honor. O Allah, the Owner of wealth and enrichment. There is no god but You, the Supporter of the refugees, the Helper of those who appeal for help, and Granter of security for panic-stricken. O Allah, if You had destined in the Preserved Tablet that I be unhappy, or deprived, or expelled, or poor, I beg Your Pardon, O Allah, to remove with Your grace my unhappiness or deprivation, or expulsion, or poverty.”

There are some other words that have been reported to be included in this supplication. These are “O my Lord! By Your greatest turning towards Your servants on the 15th night of Sha`ban, in which every wise command is decided and made clear, grant me such-and-such …” This addition is made by Sheikh Ma’ Al-`Aynayn Ash-Shanqiti in his book Na`t Al-Bedayat.

This supplication was not reported to have been said by the Prophet (peace and blessings be upon him). It was, rather, reported to have been said by `Umar ibn Al-Khattab and `Abdullah ibn Mas`ud (may Allah be pleased with both of them). `Umar was one of the rightly–guided caliphs whose tradition the Prophet (peace and blessings be upon him) ordered Muslims to hold fast to. Besides, the Prophet (peace and blessings be upon him) ordered Muslims in another hadith to follow in the footsteps of `Umar ibn Al-Khattab and Abu Bakr As-Siddiq. The Prophet (peace and blessings be upon him) also ordered Muslims to follow the guidance of his Companions in general.

But we are not certain that this supplication was really said by `Umar and Ibn Mas`ud and that it was received with no opposition on part of the other Companions. We are also not certain of the authenticity of what Ibn `Umar and Ibn Mas`ud were reported to have said about the significance of this supplication, namely, “To any servant who offered this supplication Allah granted what he wanted.” (Ibn Abi Shaybah and Ibn Abi Ad-Dunyah)

Anyway, whatever supplication one offers, it should not contradict the beliefs and rulings we are ordered to abide by. There are two points in this supplication discussed by scholars in detail. The first is regarding one’s asking Almighty Allah to remove one’s bad fortunes from the Preserved Tablet (a record that contains Almighty Allah’s established knowledge about His creation).

Explaining this part of the supplication, scholars said that what is written in the Preserved Tablet is what Almighty Allah has destined for His servants. This includes what is conditional on a certain supplication a servant offers or an act he accomplishes, and includes also what is not conditional, i.e., the decided-upon destinies. Hence, supplications and good deeds benefit one as far as the conditional destinies are concerned, while their effectiveness with regard to the unconditional destinies is manifested only in lessening the burden one may bear in this respect, as said in the supplication “O Allah! I do not ask You to change what You have already destined for me, but I beseech You to lessen its burden on me.” It was also reported that the Prophet (peace and blessings be upon him) said, “Supplications have positive effects on what has already taken place and what has not yet.”

The Companions asked the Prophet (peace and blessings be upon him), “For what should we work now, for that which has already been destined or that which is yet to come?” He (peace and blessings be upon him) replied, “For that which has already been destined.” The Companions said, “Why should we work then?” He (peace and blessings be upon him) said, “Carry on doing (good) deeds, for everybody will find it easy to do such deeds as will lead him to his destined place for which he has been created.”

In another version of this hadith, the Companions asked the Prophet (peace and blessings be upon him), “Shall we not depend upon what has been written for us and give up deeds?” He (peace and blessings be upon him) said, “He who is destined to be among the happy (in the Hereafter) will find it easy to do the deeds characteristic of such people, while he who is destined to be among the miserable ones will find it easy to do the deeds characteristic of such people. So carry on doing (good) deeds, for everybody will find it easy to do such deeds as will lead him to his destined place for which he has been created.” Then he (peace and blessings be upon him) recited Almighty Allah’s words: (As for him who giveth and is dutiful (toward Allah) and believeth in goodness, surely We will ease his way unto the state of ease. But as for him who hoards and deems himself independent,‏ and disbelieves in goodness, surely We will ease his way unto adversity. His riches will not save him when he perished) (Al-Layl 92: 5-10).

However, according to Al-Alusi and Al-Fakhr Ar-Razi, some scholars did not approve of this explanation of the possibility of removing something from the Preserved Tablet. They say that this may be done in the records that angels write concerning people’s deeds, not in the Preserved Tablet.

The second point discussed by scholars with regard to this supplication is concerning saying that the 15th night of Sha`ban is the night on which every wise command is decided and made clear, quoting this from a Qur’anic verse. This is not right. According to `Ikrimah, he who says so cannot be right at any rate, for the verse referred to here states clearly that the Qur’an was revealed in this night. It is established that the Qur’an was revealed in the Night of Qadr and this night is in the month of Ramadan, not Sha`ban.
there is also a da`if  hadith to the effect that the time of death prescribed for one may be postponed from Sha`ban to another Sha`ban to the extent that one might marry and have a child, while his name had been among the dead in the Preserved Tablet (Al-Mawahib Al-Laduaniyyah, vol. 2, p. 260). Though this hadith is da`if, some scholars tried to reconcile between its meaning and the other religious texts that seem to contradict it, saying that what takes place in Sha`ban is copying what is in the Preserved Tablet into the records that angels write, [and therein may occur the change].

But I believe that there is no need for one to resort to such controversial supplications, as there are many other supplications from the Qur’an and the authentic hadiths that one may offer sincerely in one’s prayers.