Why do we have number of sects in Islam, and when they all started? Like other religions we have 72 sects in Islam Why? Was it there during the Prophet’s time & the rightly guided caliphs? Please clarify in detail at the earliest. Jazak Allah Khayran

Prophet Muhammed's community is made up of ath-thaqalayn (man and jinn). This is because he was sent to all people — those who accept Islam are those who respond to his call and are therefore saved [from Hell-Fire).
The hadith reported by Anas [may Allah be pleased with him], that the Prophet [peace be upon him] said: "My community will divide into seventy something groups; all of them will be in Paradise except for the disbelievers." After listing these groups and mentioning the hadtih that state that 72 groups will be in Paradise and a single group will be in Hell-Fire and that that 72 groups will be Hell-Fire and a single one will be saved, Al-Shams Muhammad Ibn Ahmad al-Bishari al-Maqdisi mentioned in Ahsan at-Taqasim that the latter is the more well known hadith while the chain of transmission of the former is the sounder. For this reason, the luminary Ibn al-Wazir challenged the hadith in general and the additional statement in particular because they do not only misguide the community but lead to accusations of disbelieve.
- In his book Al-'Awasim, Ibn al-Wazir (may Allah have mercy on him) spoke about the excellence of this ummah and warned against any involvement in accusing any Muslim of disbelief. He said, "Do not be misled by the [phrase] "all of them will be in Hell-fire except for one" because it is an invalid and baseless addition and it is not far-fetched [to say] that it was introduced by unbelievers."
- He [further] wrote that Ibn Hazm said, "These are forged reports: they are neither classed as mawquf [attributed to any of the Companions] nor marfu' [raised to the Prophet]. All hadiths disparaging the Qadariya, the Murj`iya and the Ash'ariya are likewise weak.
- Scholars in the past and in recent times have refuted the hadith due to its chain of transmission while others rejected it due to its text and meaning. Muhammad Ibn Hazm refuted the allegations of those who accuse others of disbelieve due to differences in belief and based his refutation on some evidences which they mentioned in this respect. From among the things which they used to substantiate their accusations of disbelief, he mentioned two hadith which they attribute to the Prophet peace be upon him,
1. "-The Qadariyya and the Murji`iya are the Magi of this community."
2. "-This community will be divided into seventy something groups. All will be in Hell-Fire except one which will enter Paradise."
Abu Muhammad said that, based on their chains of transmission, these two hadiths are unauthentic. Such types of hadiths cannot be used as evidence according to the opinion of the hadith scholars who acknowledge hadith al-khabar al-wahid let alone those who do not acknowledge them!
In his book Al-'Awasim wa Al-Qawasim, The Yemeni Jurist, imam and supporter of the sunnah, Mohammed Ibn Ibrahim al-Wazir, reconciled intellectual and textual evidences and enumerated the hadiths narrated by Mu'awiyah (may Allah be pleased with him) including the 8th hadith on the ummah dividing into 70 something groups all of which will be in Hell-fire except for one. He commented and said, "The chain of transmission of this hadith includes a nasibi [i.e. a Shi'ite person who hates the Sunnis] and thus the hadith is unauthentic." At-Tirmidhi reported the same hadith through Abdullah Ibn 'Amr Ibn al-'As (may Allah be pleased with them both) and said, "It is a gharib [singular] hadith. At-Tirmidhi mentioned this hadith in the book Al-Iman through al-Ifriqi whose name is Abdar-Rahman Ibn Ziyad Ibn Abdullah through Ibn Yazid. Ibn Majah narrated a similar hadith on the authority of 'Awf Ibn Malik and Anas. He continued and said that these narrations do not meet the conditions of hadith sahih and, therefore, Bukhari and Muslim did not record any of them. From these hadiths, At-Tirmidhi declared Abu Huraira's report through Muhammad Ibn 'Amr Ibn 'Alqama which does not include "all of them will enter Fire except one group" as authentic. Ibn hazm said, "The author of Al-Badr al-Munir mentioned that this additional statement is fabricated." In his interpretation of the verse,
… or to confuse you [so you become] sects and make you taste the violence of one another. [Al-An'am, 65).
That it was reported in a hadith with multiple chains of transmission through the Prophet that he said, "This community will divide into 73 groups; all of them will enter Hell-Fire, except for one". Ibn Kathir did not add anything to the hadith and did not classify it either as authentic or fair although he elaborated on the interpretation of the verse by mentioning hadiths and non-prophetic narrations related to it.
After mentioning Ibn Kathir's opinion on the hadith, Imam al-Shawkani said, "As for the additional phrase "all of them will enter Hell-Fire except for one", some hadith scholars have maintained that it is weak. Ibn Hazm, on the other hand, described it as fabricated."
Despite the fact that some scholars have declared this hadith fair [hasan] like Ibn Hajar or authentic [Sahih] like Sheikh al-Islam Ibn Taymiya due to its multiple chains of transmission, it does not stand as proof on the division of the community, both in manner and number, to be considered of permanent application until the day of Judgment. The existence of such sects at any given time, suffices as proof for the authenticity of the hadith. These groups may exist and, when they do, they will be overwhelmed by truth and then perish, never to return. This is what actually happened to many of such deviant groups, some of which perished and are no more.
This hadith indicates that all of these sects are attributed to the Prophet's ummah—i.e. they are Muslims. This is proved by the words, "my ummah will divide" and means that despite their innovation, these sects do not leave Islam nor are they omitted from the Muslim community. And the fact that they will be in (Hellfire) does not mean that they will be among its eternal dwellers like the disbelievers; rather, they will be dealt with like the disobedient believers. One of the pious believers, angels or Prophets may intercede for them (by the leave of Allah) or they may have made good deeds or suffered calamities which may obliterate their sins and ward off torture.
Allah Almighty may forgive them out of His grace and bounty, especially if they endeavored to reach truth but failed and deviated from the right path. Allah forgives people of this community their mistakes, things they do out of forgetfulness or by coercion.
Ahlu Al-Sunnah Wa Al-Jama' [Sunnis] are those who followed the moderate approach in Islam. This is represented by the noble Azhar throughout centuries through Islamic law [Shari'ah], creed ['Aqida] and behavior as follows:
-Shri'ah
Al-Azhar depends on the four main followed Sunni schools of Jurisprudence [fiqh] and likewise takes from other schools since Islamic fiqh is flexible and extensive.
- 'Aqida
Al-Azhar follows the 'Aqida of Ash'aris and Maturidis which is that of Ahlu Al-Sunnah Wa Al-Jama'.
- Behavior
The Sunni Sufism which is bounded by the Qur'an and Sunnah and followed by the predecessor and successor generations. This means politeness with Allah Almighty, purifying oneself and elevation in ranks of perfection and sincerity.