The companions of the Prophet and the scholars of Islam following them were well aware of this fact and subsequently condemned all types of innovations and warned people against them, as has been expounded in the works of those who wrote on the topics of Sunnah and Bid'ah, like lbn Waddah, AI Turtusi, Abi Shama and others.
Among the things which people innovated is the celebration of the night of 15th Sha'ban and the singling out of this particular day for fasting, although there is no proof in support of this. There are certain Hadiths regarding this matter all of which are so weak that they cannot be used as justification. Hadiths concerning the virtues of prayer on this night are Mawdu' (fabricated) as explained by scholars, some of whom we will quote later on Insha-Allah. Although there are certain traditions attributed to the predecessors and some Syrian scholars in support of this issue, the vast majority of scholars of the Ummah regards the celebrating of this night as a Bid'ah. They also agree that all the hadiths regarding this matter are Da'eef (weak), and some of them are fabricated. Among the scholars who draw attention to this point is AI-Hafiz lbn Rajab al-Hambali in his book Lata'if AI Ma'arif and in others. Weak hadiths may only he used to support those matters of Ibadah (worship), which are already based on authentic proofs. Hence any Da'eef hadith used to support this practice are irrelevant. This important principle regarding the use of Da'eef Hadiths has been elucidated by Shaykh ul-lslam lbn Taymiyyah (Rahimahullah).
There is a consensus among all the scholars of Islam that, whenever a dispute arises amongst the people, then it incumbent upon them to refer to the Holy Qur'an and the authentic Sunnah of the Prophet (SAW) and whatever the verdict is from either of these sources. That is the Shari'ah which must be followed, and whatever opposes them must be rejected. Anything considered as 'Ibadah, which has no mention in the Qur'an or the authentic Sunnah is a Bid'ah and therefore practising it, let alone preaching it's virtues, is forbidden.

Oh you who believe! Obey Allah and obey the messenger and those charged with authority among you. If you differ in anything among yourselves refer it to Allah and his messenger, if you do believe in Allah and the Last Day; that is best and most suitable for final determination. (Surah An Nisa' 4:59)
Whatever it be wherein you differ, the decision thereof is with Allah (Surah AI-Shura 42:10)
Say: if you do love Allah, follow me; Allah will love you and forgive you your sins. (Surah Aali-'Imran 3:31)
But no, by thy Lord, they can never attain real faith until they make thee the judge in all disputes among them, and find in their souls no resistance against thy decisions, but accept them with the fullest conviction. (Surah An-Nisa' 4:65)

Apart from this, there are many ayats (verse) in the Holy Qur'an which make it compulsory to refer all disputes to the Qur'an and the authentic hadiths. Then be satisfied with the verdict, which is actually Iman, and is beneficial to mankind in this world and far better regarding the ultimate outcome in the hereafter.
Hafiz ibn Rajab remarked in his book Lata'if Al-Ma'arif after his previously quoted statement, that, 'Some of the followers of the companions like Khalid bin Ma'dan and Makhul and Luqman bin 'Amir used to respect the 15th of Sha'ban by offering extra prayers at night. It is said that they were influenced by certain Judaic traditions. (All those who hold this night in esteem are in fact following this isolated tradition). Gradually this practice spread to many parts of the Muslim World and thus created confusion and differences of opinion among the people. Some accepted it, among whom were zealous worshippers from Basra, but most of the scholars of Hijaz rejected it and condemned it, like 'Ata and lbn Abi Mulaika, as did all the scholars of Madina as reported by, Abdur Rahman bin Zayd bin Aslani and the Maliki School of Fiqh (thought) and all Agreed as Bid'ah. However, the scholars of Syria (who supported this issue) differed in how the 15th of Sha'ban should be celebrated. The first group regarded the celebration of this night in the mosque collectively as Mustahab (recommended). Among them were Khalid bin Ma'dan, Luqman bin 'Amir and others, who would dress specially for the occasion and hasten to the masque wherein they would remain awake throughout the night. Ishaq bin Rahawayhi endorsed this practice and said that celebrating this night collectively in the mosque is not a Bid'ah (reported by Harb Al-Kirmani in his treatise on religious opinions).
However, another group regarded celebrating this night through prayer, story-telling and supplication collectively in the mosque as Makhruh (discouraged) and it was not Makhruh for a person to pray individually at home and this is the opinion of Awza'i, the Imam, Faqih and scholar of Syria, and this is the nearest to the truth.' He (Ibn Rajab) further stated that there was no report from Ahmad bin Hanbal regarding the 15th of Sha'ban, but there are those who tried to deduce from his opinions that there was a recommendation in celebrating this night. However, according to another view it was deduced that there was no recommendation, on the basis that Ahmad bin Hanbal stated that there was no evidence to support celebrating the nights of the two 'Eids. A further view reported that Ahmad bin Hanbal regarded the celebration of this night as Mustahab, because Abdur Rahman bin Zayd used to practise it and he is from among the Tabi'een (Second generation of Muslims). lbn Rajab continues that there is absolutely evidence from either the life of the Prophet (SAW) or any of his companions regarding 15th Sha'ban, but rather from the aforementioned Tabi'een and Syrian scholars. Here, Ibn Rajab is emphasising that celebrating 15th Sha'ban was completely unknown in the time of the Prophet (SAW) and his companions. Awzai's view that one can celebrate this night by offering prayers individually at home and lbn Rajab's supporting for this view is strange and weak, because no Muslim is allowed to innovate anything in the religion that is not established by the proofs from Shari'ah, whether the practice is done individually or collectively, openly or secretly, taking into consideration the comprehensive statement of the Prophet (SAW), 'Anyone who does an action which we have not commanded, it is to be rejected (Muslim), ... and other proofs regarding Bid'ah and warnings against it.
The Imam Abu Bakr AI-Turtusi has remarked in his book AI-Hawadith Wal Bid'ah that lbn Waddah has reported from Zaid bin Aslam as saying, None of our scholars (Fuqhaha) gave any consideration or attention to the 15th Sha'ban nor the hadith of Makhool, neither did they give this night precedence over other nights. lbn Mulaika bin Zayyad AI-Numayri was asked whether or not the reward of the night of 15th Sha'ban was equal to that of Lailat AI-Qadr. He replied that were anyone to utter this in front of him he would strike them with a stick.

The great scholar Ash-Shawkani has stated in his book AI Fawa'id Al-Majmu'ah that, the hadith, '0 Ali, whoever prays one hundred rak'ah on the night of the 15th Sha'ban reciting Surah al-Fatihah and Surah al-lkhlas 11 times, certainly all his needs will be fulfilled', is fabricated as is self evident from its wording and the unlimited reward claimed. Furthermore all the transmitters are also unknown. In his, AI-Mukhtasar he stated, The hadith relating to the prayer in the night of 15th Sha'ban is Batil (false) and the hadith of lbn Hibban saying, '0 Ali, stay awake during the night of 5th Sha'ban and fast the following days' is Daeef.

It is reported in the book of La'li that praying one hundred rak'ah on the 15th Sha'ban while reciting Surah al-Ikhlas ten times in each rak'ah is all but fabricated due to the fact that in all three narrations of this hadith the transmitters are either weak or unknown. In the hadith which states for one to read twelve rak'ah reciting Surah al-Ikhlas thirty times in each rak'ah is fabricated. Another hadith recommending fourteen is also fabricated.

A good number of Fuqhaha have been deceived by these Hadiths like the author of Ihyaa Ulum ad-Deen (Imam AI-Ghazali) and others and some commentators on the Qur'an.
All the hadiths pertaining to prayers on this night are either false or fabricated regardless of their criteria. My last statement does not contradict At-Tirmidhi's hadith in which A'isha reports the Prophet (SAW) visiting Jannat al-Baqi (famous grave-yard of Madina) on the night of 15th Sha'ban in which Allah (SWT) descends to the lowest Heaven to forgive the sins, even if they were to exceed the number hairs on the sheep of the tribe of Kalb, as I was referring to specific prayers offered on the night of 15th Sha' ban. It is worth noting that this hadith, as well as being weak, also has a break in its chain of narrators.

AI-Hafiz AI-'Iraqi said the hadith concerning prayers on this night is falsely attributed to the Prophet (SAW) and It is a lie against him.

Imam An-Nawawi, in his book AI-Majmuah says:
The prayer known as Salat-ar-Raghaib which consists of twelve rak'ah offered between Maghrib and 'Isha on the first Jumu'ah of the month of Rajab, and the one hundred rak'ah offered on the 15th Sha'ban are the worst kind of Bid'ah.

One should not be deceived by the fact that these prayers have been mentioned in the book of Qut al-Quloob and lhyaa 'Ulum ad-Deen or the hadith quoted in there because they are false. Similarly, one should not be fooled by those Fuqhaha who fail to obtain a clear understanding of this issue and then proceed to write books recommending these prayers, no doubt they are at fault.
Imam Abu Muhammad Abdur-Rahman bin Isma'il AI-Maqdasi has written an extremely competent book on this topic refuting both the above mentioned books. Furthermore, the refutations of countless scholars on the same are too numerous to be quoted. However, I hope that what I have already quoted is sufficient for the sincere seeker of truth. It is manifestly obvious from Qur'an, hadith and the quotations of scholars that celebrating the 15th Sha'ban, offering special prayers or any specific 'Ibadah on this night and fasting the following day is the most contemptible type of Bid'ah innovated after the period of the companions.

Abu Hurayrah reported the Prophet (SAW) as saying:
Don't single out the night of Jumu'ah for praying its day for fasting except if the day happens to coincide with ones habitual fasting. (Muslim)

From this hadith we can deduce that had any night been singled out for special prayers, it would have been the night of Jumu'ah, for according to authentic hadiths this Is the best of days on which the sun rises. It is evident that since the Prophet (SAW) forbade singling out the night of Jumu'ah for any special prayer, why should any other night be preferred for this without reliable proof.
Since special prayers in the night of Lailat ul-Qadr and the other nights of Ramadan are sanctioned by the Shari'ah, the Prophet (SAW) has left personal examples as reported in the Two Sahih (Bukhari & Muslim)
The Prophet (SAW) said that whoever prays in the night of Ramadan with sincere faith and hope of reward, Allah will forgive him all his previous sins. Similarly, had there been any special prayers or celebrations sanctioned by the Shari'ah for the 15th Sha' ban, the first Jumu'ah of Rajab or for the night of Mi'raaj, the Prophet (SAW) would definitely have either mentioned or practised them himself. Had this practice occurred, it would certainly have been reported by the companions and hence transmitted to the Ummah, as they are the best of people and most sincere after the Prophets, may Allah be please with them.

It has now been made perfectly clear from the quotations of the scholars that no evidence can be attributed to the Prophet (SAW) or his companions regarding the virtue of the first Jumu'ah of Rajab and the 15th Sha'ban, so It must be concluded that these two nights are something innovated in Islam and singling them out with any particular 'Ibadah is the worst type of Bid'ah. Similarly, the 27th of Rajab, which some people believe to be the night of Isra and Mi'raaj', should not be celebrated. It is forbidden to single out this night for specific 'Ibadah or celebrate it in any form or manner as proven from the above mentioned proofs.

It is noteworthy that the night of the Prophet (SAW) journey is not known according to the genuine opinions of the scholars and claiming that 27th Rajab is the night of the Isra and Mi'raaj is a false claim as it has no foundation in the authentic hadiths. The best of things are the predecessors on guidance and truth, and the worst of things are those innovated.

... It has now been made perfectly clear from the quotations of the scholars that no evidence can be attributed to the Prophet (SAW) or his companions regarding the virtue of the first Jumu'ah of Rajab and the 15th Sha'ban, so It must be concluded that these two nights are something innovated in Islam and singling them out with any particular 'Ibadah is the worst type of Bid'ah. Similarly, the 27th of Rajab, which some people believe to be the night of Isra and Mi'raaj', should not be celebrated. It is forbidden to single out this night for specific 'Ibadah or celebrate it in any form or manner as proven from the above mentioned proofs.

It is noteworthy that the night of the Prophet (SAW) journey is not known according to the genuine opinions of the scholars and claiming that 27th Rajab is the night of the Isra and Mi'raaj is a false claim as it has no foundation in the authentic hadiths. The best of things are the predecessors on guidance and truth, and the worst of things are those innovated.

I ask Allah (SWT) to give us the strength to hold on to the Sunnah and remain steadfast on it and be cautious of anything which opposes it. Allah (SWT) is the Most Generous and Most Benevolent. Peace and blessings be upon his slave and Messenger, Muhammad (SAW).

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