“Naturally, the expression "Ahl al-Sunnah" was unknown in the early days of Islam.”
The expression "Ahl al-Sunna" is reported from Ibn `Abbas and Ibn `Umar by al-Lalika'i in Sharh Usul I`tiqad Ahl al-Sunna; Muslim narrates it from Muhammad ibn Sirin in the Muqaddima to his Sahih; and al-Darimi in his Musnad from al-Hasan al-Basri. This is not to mention the Mujtahid Imams and those of the generation-layer immediately preceding them.
I could look up al-Suyuti's compilation Miftah al-Janna fi al-Ihtijaj bis- Sunna and the late Dr. `Abd al-Khaliq Abd al-Ghani's Hujjiyyat al-Sunna for more reports, but this is probably enough to put to rest the false assumption that the expression was unknown in the early days of Islam
""Hold on to my Sunnah and the Sunnah of the Rightly Guided Caliphs after me. Hold on to it firmly.
Reported by Ahmad Ibn Hanbal Abu Dawud, at-Tirmidhi who said it is a good and sound hadith, and Ibn Majah)
Hold fast to my Sunnah and the Sunnah of the Rightly Guided Caliphs.
(Abu Bakr, Umar, Uthman and Ali (may Allah be pleased with them).
Clamp your molars upon it, avoid new novelties, for every novelty is an innovation, and every innovation is misguidance.
Sahih Hadith recorded in (no. 4590), Sunan al-Tirmidhi (5/43, no. 2676), Sunan Ibn Majah (1/15-6, no. 42), Sunan al-Darimi (no. 96), Ibn Abi Aasim in al-Sunnah (no. 54), Imam Ahmad ibn Hanbal in his Musnad (4/126), al-Hakim in al-Mustadrak (1/95-6) and Ibn Hibban in his Sahih (1/166, no. 5).
Allah will never let my Ummah agree upon misguidance, and the hand of Allah is over the group (Jama'ah), so follow the great mass of believers (Sawad ul-'Azam), and whoever dissents from them departs to hell.
A narration authenticated and reported by al-Hakim (1/116), and al-Dhahabi agreed with him. A very similar report has been recorded by al-Tirmidhi (4/2167). Imam al-Munawi said in commentary to Tirmidhi's Hadith: (Allah's hand is over the Jama'ah) meaning his protection and preservation of them, signifying that the collectivity of the people of Islam are in Allah's fold, so be also in Allah's shelter, in the midst of them, and do not separate yourselves from them. (And whoever descents from them departs to hell) meaning that whoever diverges from the overwhelming majority concerning what is lawful or unlawful and on which the Community does not differ has slipped off the path of guidance and this will lead him to hell. (see Imam al-Azizi's: al-Siraj al-Munir Sharh al-Jami us-Saghir, 3/449, cf. Reliance of the Traveller, p. 25).
. Fa`tasimu bi hablillahi jami`an wa la tafarraqu
"Hold fast to the rope of Allah, all of you, and do not split into factions" (3:103).
2. Wa la tafarraqu illa min ba`di ma ja'ahum al-`ilmu baghyan
"And they were not divided until after the knowledge came unto them, through rivalry among themselves" (42:14).
3. Ya ayyuha al-ladhina amanu ati`ullaha wa ati`u al-rasula
wa uli al-amri minkum
"O you who believe, obey Allah and obey the Prophet and those of authority among you" (4:59).
4. Wa man yushaqiq al-rasula min ba`di ma tabayyana lahu al-huda wa yattabi` ghayra sabil al-mu'minin nuwallihi ma tawalla wa nuslihi jahannama wa sa'at masira
"Whoever contraverts the Messenger after guidance has become clear to him and follows other than the believers' way, We shall give him over to what he has turned to and expose him unto hell, and how evil an outcome!" (4:115).
5. Wa asbir nafsaka ma` al-ladhina yad`una rabbahum bi al-ghadati wa al-`ashiyyi yuriduna wajhah wa la ta`du `aynaka `anhum turidu zinat al-hayat al-dunya wa la tuti` man aghfalna qalbahu `an dhikrina wa ittaba`a hawahu wa kana amruhu furutan
"Restrain thyself along with those who call upon their Lord at morning and evening, seeking his pleasure; and let not thine eyes overlook them, desiring the pomp of this worldly life; and obey not him whose heart We have made heedless of Our remembrance, who followeth his own lust and whose case has gone beyond all bounds." (18:28)
6. Ati`u Allaha wa ati`u al-rasula wa uli al-amri minkum...
"Obey Allah and obey the Messenger and those who are in charge of affairs among you. Should you happen to dispute over something, then refer it to Allah and to the Messenger." (4:58-59)
7. Alaykum bi al-jama`a fa innallaha la yajma`u ummata Muhammadin `ala dalala
"You have to follow the Congregation for verily Allah will not make the largest group of Muhammad's Community agree.
Ibn Abi Shayba relates it with a sound chain.
8a. La yajma`ullahu ummata Muhammadin `ala dalala
"Verily Allah will not make Muhammad's Community agree on error
al-Hakim narrated it in the Mustadrak (1:116, 177) with a sound (sahih) chain.
8b Inna Allaha la yajma`u ummati -- aw qala: ummata Muhammadin --`ala dalalatin wa yadullahi ma` al-jama`a
"Verily Allah will not make my Community -- or Muhammad's Community -- agree on error, and Allah's hand is with the largest Congregation." Tirmidhi said: "And the meaning of "jama`a" according to the people of knowledge is: the people of jurisprudence, learning, and hadith
]Tirmidhi (gharib) #2256, Cairo ed. `Aridat al-ahwadhi (11:9).
9. Man arada minkum bi habuhat al-jannati fal yulzim al-jama`at
"Whoever among you wants to be in the middle of Paradise, let him cling to the Congregation
Tirmidhi related it and said it is sound (sahih).
10. Inna al-shaytana dhaybun ka dhayb al-ghanam ya'khudh al-shat al-qasiya wal-najiya fa iyyakum wal-shu`aab wa `alaykum bil-jama`ati wal-`aammati wal-masjid
"Shaytan is a wolf like the wolf that preys on sheep, taking the isolated and the stray among them; therefore, avoid factionalism and keep to the Congregation and the collective and the masjid
Ahmad relates it through Mu`adh and through Abu Dharr, the two chains being respectively fair [hasan] and sound [sahih] according to Haythami in Majma` al-zawa'id
11. Inna ummati la tajtami`u `ala dalalatin fa idha ra'aytum al-ikhtilaf fa `alaykum bi al- sawad al-a`zam.
"My Community shall never agree upon misguidance, therefore, if you see divergences, you must follow the greater mass or larger group
Ibn Majah (2:1303 #3950) from Anas with a weak chain. Ahmad narrates it mawquf through three sound chains to Abu Umama al-Bahili and Ibn Abi Awfa. However, it is marfu` to the Prophet from Abu Umama by Ibn Abi Shayba in his Musannaf as well as Ibn Jarir al-Tabari, the latter two's narration stating that Abu Umama heard this from the Prophet up to seven times. Bayhaqi in al-Madkhal narrates something similar from Ibn `Abbas.
11a Lan tajtami`a ummati `ala dalalatin fa `alaykum bi al-jama`ati fa inna yadullahi `ala al-jama`a.
"My Community shall not agree upon misguidance. Therefore, you must stay with the Congregation, and Allah's hand is over the Congregation.
Tabarani narrated it with two chains from Ibn `Umar, one of which is sound (sahih). See Haythami, Majma` al-zawa'id, chapter on the obligation to stay with the Congregation.
12. Innallaha qad ajara ummati min an tajtami`a `ala dalala
"Verily Allah has protected my Community from agreeing upon error
Ibn Abi `Asim narrated it in the Sunna
13. Kana al-nasu yas'aluna Rasulallahi `an al-khayr wa kuntu as'aluhu `an al-sharr...qultu ya rasulallahi sifhum lana [ayy al-du`at `ala abwabi jahannam] qala hum min jildatina wa yatakallamuna bi alsinatina qultu fa ma ta'murni in adrakani dhalik al-yawm? qala tulzim jama`at al-muslimin wa imamahum
"People used to ask the Prophet about the good and I used to ask him about the evil... I said: O Messenger of Allah, describe them to us [the callers at the door of the fire]. He said: They are of our complexion and they speak our very language. I said: What do you order me to do if that day reaches me? He said: You must keep to the Congregation of Muslims and to their leader.
Bukhari and Muslim on the authority of Hudhayfa ibn al-Yaman.
14 Yadu Allah `ala al-jama`a
"Allah's hand is over the group
-Munawi said: "Allah's hand is over the group means His protection and preservation for them, signifying that the collectivity of the people of Islam are in Allah's fold, so be also in Allah's shelter, in the midst of them, and do not separate yourselves from them. Whoever diverges from the overwhelming majority concerning what is lawful and unlawful and on which the Community does not differ has slipped off the path of guidance and this will lead him to hell.
al-Munawi, Sharh al-Jami` al-saghir 3:449.
14a. Yadu Allah `ala al-jama`at wa man shadhdha shadhdha ila al-nar.
"Allah's hand is over the group, and whoever dissents from them departs to hell
Tirmidhi (gharib) from Ibn `Umar, al-Hakim both from Ibn `Umar and Ibn `Abbas, and Ibn Jarir from Ibn `Umar.
14b. Yadu Allah `ala al-jama`a, ittabi`u al-sawad al-a`zam fa innahu man shadhdha shadhdha ila al-nar.
"Allah's hand is over the group, follow the largest mass, for verily whoever dissents from them departs to hell
Narrated by al-Hakim and al-Tabari from Ibn `Abbas, and al-Lalika'i in al-Sunna and al-Hakim also narrated it from Ibn `Umar.
14c Man faraqa al-jama`ata shibran mata maytatan Jahiliyya.
"Whoever leaves the Community or separates himself from it by the length of a span, dies the death of the Jahiliyya (period of ignorance prior to Islam)";
Muslim (Imara #55) through Ibn `Abbas. Muslim relates it with slight variations through three more chains. Ibn Abi Shayba also relates it in his Musannaf
15. Abu Ghalib said that during the crisis with the Khawarij in Damascus he saw Abu Umama one day and he was crying. He asked him what made him cry and he replied: "They followed our religion," then he mentioned what was going to happen to them tomorrow. Abu Ghalib said: "Are you saying this according to your opinion or from something you heard the Prophet say?" Abu Umama said: "What I just told you I did not hear from the Prophet only once, or twice, or three times, but more than seven times. Did you not read this verse in Al `Imran: The day faces will be white and faces will be dark..."? (3:106) to the end of the verse. Then he said: I heard the Prophet say: "The Jews separated into 71 sects, 70 of which are in the fire; the Christians into 72 sects, 71 of which are in the fire; and this Community will separate into 73 sects, all of them are in the fire except one which will enter Paradise." We said: "Describe it for us." He said: "The Sawad al-a`zam."
Haythami said in Majma` al-zawa'id: Tabarani narrated it in al-Mu`jam al-kabir and al-Awsat, and its narrators are trustworthy (thiqat).
16. Sataftariqu ummati `ala thalathat wa sab`ina firqatin kulluhum fil nari ila millatin wahidat, qalu man hiya ya rasulallah, qala ma ana `alayhi wa as-habi
"My Community will split into seventy-three sects. All of them will be in the fire except one group. They asked: Who are they, O Messenger of Allah? He said: Those that follow my way and that of my companions
Tirmidhi, Abu Dawud, and al-Darimi related it.
IT IS VERY CLEAR FROM THE ABOVE EVIDENCE THAT ALLAH SUBHANAHU WA TAALA COMMANDED US TO FOLLOW HIS PROPHET AND PROPHET TOLD US TO FOLLOW HIS SUNNAH, THE JAMMAH (LARGER GROUP) AND HIS COMPANIONS AFTER HIM.
HIS COMPANIONS CALLED THEM SELF FROM AHLUS SUNNAH.
QURAN TELLS US “ASK THEM THOSE WHO KNOW”
ALL THE SCHOLRS IN THIS UMMAH ARE FROM THE MAIN BODY OF MUSLIM UMMAH AND THEY HAVE CALLED IT AHLUS SUNNAH WAL JAMAH!.