The Arabic term ‘Eid denotes recurrence and is used to refer to celebratory occasions (of assembly) which customarily recurs annually, monthly, weekly or so on.

It is not permissible to celebrate any given day or place that is not prescribed by the Sharee’ah by performing a special worshipful act, (holding a) celebratory assembly, or observing specific customs. The prohibition is rather emphasized, and its gravity increases if such unprescribed celebration happened to coincide with the festivals and celebratory assemblies of the disbelievers, polytheists, Jews, and Christians, because it involves imitation of their actions and outward appearances, which ultimately leads to imitation of their inward beliefs).

It was narrated on the authority of Thaabit ibn Al-Dahhaak (may Allah be pleased with him) that a man took a vow to slaughter a camel at Buwanah during the lifetime of the Prophet ?. He went to the Prophet ? and said: ‘I have taken a vow to sacrifice a camel at (a place called) Buwanah.’ He ? asked: ‘Did the place contain any idol worshipped in pre-Islamic times?’ They said: ‘No.’ Thereupon, he ? asked: ‘Was any pre-Islamic festival observed there?’ They replied: ‘No.’ He ? said: ‘Fulfil your vow, for a vow to do an act of disobedience to Allah must not be fulfilled, neither must one do something over which a human being has no authority.’” [379]: It was narrated by Aboo Daawood (no. 3313) with this wording, Al-Tabaraani (2/76) (1341) and Al-Bayhaqi (no. 20634). Ibn ‘Abd Al-Haadi said in ((Al-Saarim Al-Munki)) (no. 493): ‘It is Hasan Saheeh.’ It was classified as Saheeh by Ibn Al-Mulqin in “Al-Badr Al-Muneer” (9/518), Al-Albaanee in “Saheeh Sunan Aboo Daawood” (no. 3313), and Al-Waadi’i according to the conditions stipulated by Bukhaaree and Muslim in “Al-Saheeh Al-Musnad” (193), and its chain of transmission was judged authentic by Al-Nawawee according to the conditions stipulated by Bukhaaree and Muslim in “Al-Majmoo’” (8/467), Ibn Hajar in “Buloogh Al-Maraam” (413), and Shu‘ayb Al-Arnaa’oot in his revision of “Sunan Aboo Daawood” (no. 3313), and Ibn Taymiyyah said in “Iqtidaa’ Al-Tareeq Al-Mustaqeem” )) (1/490): ‘This very wording, some parts of the Hadeeth, or its meaning was narrated in Saheeh Al-Bukhaaree and Saheeh Muslim, and its chain of narration was approved by Al-Bukhaaree and Muslim; all its narrators are trustworthy and well-known and the chain of narration is connected with no ‘An‘anah (none of the links of the chain are connected with the word ‘an, meaning ‘from’). Ibn Katheer said in “Irshaad Al-Faqeeh” (1/375): ‘Its chain of transmission meets the conditions stipulated by Al-Bukhaaree and Muslim. Therefore, it is forbidden to hold a celebration or a festive assembly that is unsupported by Divine textual evidence indicating its permissibility, such as the celebration of New Year’s Day, the migration, the Prophet’s birthday, the Night Journey, or the Night of the Middle of Sha’baan (the 15th of Sha’baan).

Ibn Taymiyyah said: “The term ‘Eid is a generic noun that refers to all days or places when and where a celebratory assembly is held, and all the religious acts performed in these places and times. The prohibition in this regard is not limited to their religious festivals in particular, but also includes all the time and places that they hold as sacred and have no basis in Islam, and the acts performed in these times and places as well.” [380] See: ((Iqtidaa’ Al-Siraat Al-Mustaqeem)) (2/5)
Festivals can thus be associated with specific places, times, or social occasions.

As far as the Sharee’ah ruling is concerned, the unprescribed festivals that are associated with places are of three categories:

First: Festivals to which the Sharee’ah does not assign any special virtues
This category includes all places to which the Sharee’ah does not assign any special virtues and no specific worshipful acts were prescribed to be performed therein. It is impermissible to single them out or perform specific worshipful acts in these particular places. Ibn Taymiyyah said about the unprescribed festivals that are associated with specific places: (These festivals include the places to which Sharee’ah does not ascribe specific merits or virtues and is rather held in an equal or lower standing of other places. Visiting these specific places or gathering therein to perform prayers, recite supplications, Allah’s remembrance (Thikr), or perform worshipful acts, is sheer misguidance. Moreover, if such place contains some relics of the disbelievers (Jews or Christians) or others, such act is considered worse and more heinous.” [381] See: ((Iqtidaa’ Al-Siraat Al-Mustaqeem)) (2/155)  
 
Second: Places to which the religion assigned special virtues, but no worshipful acts are prescribed to be performed therein An example of such places is the grave of the Prophet ? and the graves in general. It is impermissible to perform worshipful acts in these places. Ibn Taymiyyah said: (The second type of festivals include the places to which the religion  assigned special virtues, but there is no Sharee’ah-based reason that entails taking them as places of ritual celebration and no prayers or other worshipful acts are prescribed to be performed therein. Examples of these places are the graves of the Prophets and the righteous. The prohibition of taking graves as places of ritual celebration was narrated on the authority of the Prophet ? and the righteous predecessors). [382] See: ((Iqtidaa’ Al-Siraat Al-Mustaqeem)) (2/169)

The third type: Places where the performance of worshipful acts is prescribed, but it is not prescribed to take them as places of ritual celebration. Ibn Taymiyyah said: (As for the places where the Prophet ? performed prayers or recited supplications, it is an act of Sunnah to perform prayers and recite supplications therein, following the example of the Prophet ?, and if he ? sought performing prayer or reciting supplications on specific times, Muslims should do the same.” [383] See: ((Iqtidaa’ Al-Siraat Al-Mustaqeem)) (2/276)   Al-Suyootee: (All recurring celebratory assemblies, either weekly, monthly, or yearly, that are not prescribed by the Sharee’ah are considered religious innovations. There is a difference between unprescribed acts that are occasionally performed on unspecified times and those performed habitually on specific times, where the second would appear to emulate the prescribed worshipful acts. Ibn Mas‘ood and other Companions believed that it is disliked to gather habitually in a specific place (as a devotional act), and this was the opinion reported on the authority of Ahmad. He was asked, ‘Do you hold that it is disliked for people to gather in a specific place to supplicate Allah and raise their hands?’ He replied, ‘I do not believe this is disliked as long as it was not done deliberately, and they do not make a habit out of it to grow in number … The basic principle is Allah, Exalted be He, prescribed adequate recurring worshipful acts that are performed habitually and become fixed spiritual seasons. Introducing unprescribed assemblies or worshipful acts would be an act of defiance to the Sharee’ah and Sunnah of the Prophet ?.” [384] See: ((Al-Amr Bil-Itibaa‘ wa Al-Nahi ‘an Al-Ibtidaa‘)) by Al-Suyootee (p.: 142).

As far as the religious ruling is concerned, the unprescribed festivals that are associated with specific times are of three types:

First: Unprescribed festivals on specific times that were not held as sacred by the religion in the first place: An example of that category is the first Thursday of Rajab.

Second: Unprescribed festivals on specific times that mark the occurrence of significant events, but it does not entail considering these times spiritual seasons:

An example of that category is celebrating the anniversary of the Battle of Badr on the 17th of Ramadan. It is forbidden to perform special worshipful acts or hold celebrations, specifically on that day. Ibn Taymiyyah said: (Festivals are part of the Sharee’ah that entail compliance with the Sharee’ah rather than introducing religious innovations. The Prophet ? delivered special speeches, made covenants, and partook in great events on several days, such as: the Battle of Badr, Hunayn, Al-Khandaq (Trench), and the Conquest of Makkah, and the day of his emigration to Al-Madeenah, and his arrival to Al-Madeenah. He ? also delivered many other speeches in which he explained the rules of Islam, yet he ? did not command us to take such significant days as festivals. Those who do so are imitating the Christians who took the days of significant events that occurred to Prophet ‘Eesa as festivals, and so did the Jews. Rather, festivals are part of the Sharee’ah, and Muslims must comply with what is prescribed by Allah, Exalted be He, otherwise they would be introducing religious innovations.” [385] See: ((Iqtidaa’ Al-Siraat Al-Mustaqeem)) (p. 2\123)
Another example is celebrating the Prophet’s birthday ?.

Taaj Al-Deen Al-Fakhaanee Al-Maalikee said: (I do not know of any evidence in the Quran or Sunnah on the permissibility of celebrating the Prophet’s birthday. It has not been reported that any of the leading Muslim scholars, who were the role models, who complied with the teachings of Islam, and adhered to the views of the early Muslim generations, did so. Rather, this is a religious innovation introduced by the deviated people and those who follow their sinful desires and whims …” [386] See: ((Al-Mawrd Fee ‘Amaal Al-Mawlid)) (p. 8-10)

Ibn Baaz said: “The Prophet ? did not command us to celebrate his birthday, but it is rather a religious innovation introduced by people in recent centuries and therefore must be rejected ... Such unprescribed celebration may be substituted by studying the historical events related to his birth as part of the religious lessons about his biography as well as the historical events related to his life before and after the advent of Islam. These lessons should be held at schools, mosques, and the like, without the need to hold a celebration that is not prescribed by Allah, Exalted be He, nor His Messenger ? and is not supported by any Divine textual evidence.” [387] See: ((Majmoo’ Fataawa Ibn Baaz)) (4/289)

Third: Times that are held sacred by the Sharee’ah
Examples of this category are the Day of ‘Ashooraa’ (10th day of Muharram), the Day of ‘Arafah (the 9th of Thul-Hijjah), and the two days of ‘Eid. The celebration of these blessed times does not constitute any violation of what Allah, Exalted be He, and His Messenger ? prescribed. The celebration of these festivals associated with specific places and times may involve religious innovations which further increase in its prohibition such as visiting the graves on the days of ‘Eid, holding devotional or celebratory assemblies at the graves, or visiting Al-Aqsa Mosque to seek blessings, performing Tawaaf around ‘Arafah Mount, and other religious innovations that are not supported by any evidence in the Quran or Sunnah. As for the assemblies, they are of three types in terms of their ruling in Islam:

First: Assemblies that are unprescribed by the religion, such as the celebratory assembly on the Prophet’s birthday.

Second: Prescribed assemblies such as the congregational prayers, the ‘Eid prayers, and the like.

Third: Assemblies that are deemed prohibited by the religion such as assemblies at graveyards and shrines to perform the obligatory prayers, supplicate the dead people buried therein, or circumambulate them.

The basic principle is that these unprescribed festivals and celebratory assemblies are prohibited. The celebration of these unprescribed festivals is considered a means leading to Shirk from two aspects:

First, it involves the imitation of the disbelievers with regard to their acts and rituals which leads to the imitation of their inward beliefs, and because imitating them implies approval of their acts, which are manifestations of their disbelief and religious idolatrous rituals.

Second: celebrating these unprescribed festivals involves contravening the religion revealed to the Prophet ?, and judgment by other than what He has revealed. Accordingly, it involves Shirk in obedience. Allah, Most High, says (interpretation of meaning): Or have they other deities who have ordained for them a religion to which Allah has not consented? Quran 42:21  Therefore, it is either a means of major or minor Shirk. If it includes worshipping other than Allah, it falls under the category of major Shirk, and if it includes what is less grave than that, it falls under the category of minor Shirk. Major Shirk runs counter to Tawheed, and minor Shirk runs counter to the perfection of Tawheed. [388] See: ((Mukhtasar Al-Fataawa Al-Masriyyah by Ibn Taymiyyah)) by Al-Ba‘li (p.: 292), ((Al-Amr Bil-Itibaa‘ wa Al-Nahiy ‘an Al-Ibtidaa‘)) by Al-Suyootee (p.: 142), ((Al-Madkhal Li-Diraasat Al-‘Aqeedah Al-Islaamiyyah)) by Ibraaheem Al-Braykaan (p.: 186) )