Allah swt says in Qur’an
قُلْ إِن كُنتُمْ تُحِبُّونَ اللَّهَ فَاتَّبِعُونِي يُحْبِبْكُمُ اللَّهُ وَيَغْفِرْ لَكُمْ ذُنُوبَكُمْ ۗ وَاللَّهُ غَفُورٌ رَّحِيمٌ
1) “Say (O Muhammad to mankind): ‘If you (really) love Allah, then follow me (i.e. accept Islamic Monotheism, follow the Qur’an and the Sunnah), Allah will love you and forgive you your sins’.” [The Holy Quran, Surah al 'Imran 3:31]2) “Follow what has been sent down unto you from your Lord (the Qur’an and Prophet Muhammad’s Sunnah), and follow not any Awliya’ (protectors and helpers who order you to associate partners in worship with Allah), besides Him (Allah). Little do you remember!” [The Holy Quran, Surah al-A'raf 7:3]
3) One day as The Prophet Muhammad (PBUH) sat with his companions, he drew a straight line in the dirt, he then drew a series of line branching off from either side of it. When the companions aasked him what it meant, … he recited the following verse: “And verily, this is my straight path, so follow it, and follow not (other) paths, for they will separate you away from His (Allah’s) path.” [The Holy Quran, Surah al-A'nam 6:153] (Reported by Ibn Masood and collected by Nasai, Ahmad, and Darimi)
4) And the Prophet Muhammad (peace and blessings of Allah be upon him) said: “The most truthful of speech is the Book of Allah and the best of guidance is the guidance of Muhammad, and the most evil of things are those which are newly-invented.” And he (peace and blessings of Allah be upon him) said: “Whoever innovates anything in this matter of ours (i.e., Islam), that is not part of it will have it rejected.” (Narrated by al-Bukhari, no. 2697; Muslim)
5) According to a version narrated by Muslim, “Whoever doe anything that is not in accordance with this matter of ours (i.e., Islam), will have it rejected.”
6) Ibn e umar (r.a) said: Every innovation is an astray even if people understands it good.
ابن عمر- رضي الله عنه – : ” كل بدعة ضلالة وإن رآها الناس حسنة ” وسنده صحيح كما قال الألباني في تخريج اصلاح المساجد ص.
( Related by Ad-Darimee, Abu Shamaah (no. 39), Ibn Nasr in as-Sunnah (no. 82), al-Laalikaa’ee in Sharh Usoolul-Ftiqaad (no. 126) & Sharh I’tiqad Ahl as-Sunnah (1/92), and by al-Bayhaqee in al-Madkhal (no. 191). Its authentic; Ahkaam al-Janaa’iz (258) and Islah al-Masajid (13). Salim Al-Hilaali said: “Its isnaad (chain of narration) is as authentic as the sun!”)
7) Prophet Muhammad (PBUH) said: “…Beware of newly invented matters, for every invented matter is an innovation and every innovation is a going astray, and every going astray is in Hell-fire.” [Wa sharrul Umoori Muhdathaatuhaa, Wa kulla Bid'atin dhaialah, wa kulla dhalatin fin-naar"] (Abu Dawud and At-Tirmidhi)
8) Abdullaah Ibn Masood (r.a) – said: “Follow and do not innovate, for indeed you have been sufficed, and every innovation is misguidance.” (Saheeh. Reported in Ahmad in Az-Zuhd p. 162, Ad-Daarimee (no. 211), Al-Bayhaqee in Madkhal (no. 204), Wakee’ in Az-Zuhd (no. 315), Ibnut-Tararaanee in As-Sunnah (no. 104), Ibn Nasr in As-Sunnah (p. 23) and by Mujaahid in As-Sab’ah (p. 46))
9) Ibn ‘Abbaas(radhi-yallaahu ‘anhumaa) said:((Indeed the most detestable of things to Allaah are the innovations)).al-Bayhaqee in as-Sunan al-Kubraa (4/316)
10) Sufyaan ath-Thowree (rahima-hullaah) mentions:((Innovation is more beloved to Iblees than sin, since a sin may be repented from but innovation is not repented from)). al-Laalikaa’ee – Sharh Usool I’tiqaad Ahlis-Sunnah wal-Jamaa’ah (no. 238)
11) al-Fudayl bin ‘Iyaad (rahima-hullaah) mentions:((I met the best of people, all of them people of the Sunnah and they used to forbid from accompanying the people of innovation)).al-Laalikaa’ee – Sharh Usool I’tiqaad Ahlis-Sunnah wal-Jamaa’ah (no.267)
12) al-Hasan al-Basree (rahima-hullaah) mentions:((Do not sit with the people of innovation and desires, nor argue with them, nor listen to them)).Sunan ad-Daarimee (1/121)
13) Ibraaheem ibn Maysarah (rahima-hullaah) mentions: ((Whoever honours an innovator has aided in the destruction of Islaam)).al-Laalikaa’ee – Sharh Usool I’tiqaad Ahlis-Sunnah wal-Jamaa’ah (1/139)
14) Sufyaan ath-Thowree (rahima-hullaah) mentions: ((Whoever listens to an innovator has left the protection of Allaah and is entrusted with the innovation)). Abu Nu’aym in al-Hilyah (7/26) and Ibn Battah (no.444)
15) Imaam al-Barbahaaree (rahima-hullaah) mentions: ((The innovators are like scorpions. They bury their heads and bodies in the sand and leave their tails out. When they get the chance they sting; the same with the innovators who conceal themselves amongst the people, when they are able, they do what they desire)). Reported in ((Tabaqaatul-Hanaabilah)) – Volume 2, Page 44 and ((Manhajul-Ahmad)) Sharhus-Sunnah – Imaam al-Barbahaaree
16) Abu Haatim (rahima-hullaah) said: ((A sign of the people of innovation is their battling against the people of Narrations)). Sharh Usool I’tiqaad Ahlus-Sunnah wal-Jamaa’ah – al-Laalikaa’ee – Volume 1, Page 179
17) as-Saffaareenee (rahima-hullaah) said: ((And we are not focusing on mentioning the virtues of the people of Hadeeth, for indeed their virtues are well known and their merits are many. So whoever belittles them, then he is despicable and lowly. And whoever hates them, then he is from the backward party of the Devil)). Lawaa.ihul-Anwaar – Volume 2, Page 355
18) Imaam Abu ‘Uthmaan as-Saaboonee (rahima-hullaah) said: ((The signs of the people of innovation are clear and obvious. The most apparent of their signs is their severe enmity for those who carry the reports of the Prophet)). The ‘Aqeedah of the (Pious) Predecessors – Page 101
19) Muhammad ibn Ahmad ibn al-Qaasim related to us, saying: Ahmad ibn al-Hasan narrated to us saying: Sulaymaan ibn al-Ash’ath narrated to us, saying: ‘Abdullaah ibn Chubbi al-Anteeq narrated to us, saying: Yaws ibn Asbaat narrated to us, saying: I heard Muhammad ibn an-Nadr al-Haarithee say: ((Whoever listens to a person of innovation – and knows that he is a person of innovation – then protection is taken away from him, and he is left to himself)). al-Imaam al-Haafiz Abul-Qaasim Habatullaah ibn al-Hasan ibn Mansoor at-Tabaree al-Laalikaa’ee (d.418 A.H.) reports in his “Sharh Usool I’tiqaad Ahlis-Sunnah wal-Jamaa’ah” – Volume 1 Pages 135-136 No. 252 Source .
20) Imaam ash-Shaafi’ee (rahima-hullaah) said: The Sunnahs of the Messenger of Allaah (sal-Allaahu ‘alayhe wa sallam) reach, as well as escape from every one of us. So whenever I voice my opinion, or formulate a principle, where something contrary to my view exists on the authority of the Messenger of Allaah (sal-Allaahu ‘alayhe wa sallam), then the correct view is what the Messenger of Allaah (sal-Allaahu ‘alayhe wa sallam) has said, and it (that) is my view. Related by Haakim with a continuous sanad up to Shaafi’i, as in Taareekh Damishq of Ibn ‘Asaakir (15/1/3), I’laam al-Muwaqqi’een (2/363, 364) & Eeqaaz (p. 100)
21) Imaam Maalik (d.179 AH) said about bidah:
“Whoever thinks that there is such thing as a good innovation in Islam, has accused the Prophetصلى الله عليه و سلم of treachery because Allah said “This day I have perfected your religion…”. So what was not religion then, is not religion today” (Al-‘Itisaam as-Shaatibi 1/38)