Imam Sufyaan ath-Thawree (rahimahullah):
repeated thrice: “This religion is based upon narrations not opinions, This religion is based upon narrations not opinions, This religion is based upon narrations not opinions.” (Sharaf Ashaabul Hadeeth)
Imaam al-Awzaee (d.157H) said: “Hold fast to the narrations of the salaf, even if people were to abandon you. Beware of the opinions of the people, no matter how much they beautify it with their speech.” [Related by al-Khateeb al-Baghdadee in his excellent book Sharafu Ashaabul-Hadeeth (p.7)]
Imaam al-Asbahaanee (d.535H) said: “The sign of Ahlus-Sunnah is that they follow the Salafus-Saalih and abandon all that is innovated and newly introduced into the Deen.” [Al-Hujjah fee Bayaanil Mahajjah 1/364]
lbn Taymiyyah (d.728H) said: “There is no criticism for the one who proclaims the way (madhdhab) of the Salaf, who attaches himself to it and refers to it. Rather, it is obligatory to accept that from him by unanimous agreement (Ittifaaq) because the way (madhdhab) of the Salaf is nothing but the Truth (Haqq).” [Majmoo al-Fataawaa 4:149]
http://maktabasalafiya.blogspot.com/2011/01/some-statements-of-salaf-on-ilmul.html