It is reported that Imām Al-Awzāʿī (d157H) wrote:

O Muslims, fear Allāh and obey Him, and accept the advice of the sincere advisers and the exhortation of the exhorters, and know that this knowledge is religion, so be careful about what you do [in it] and from whom you take [it] and who you follow and who you trust your religion to. For verily, the followers of Bid’ah are all falsifiers and liars, neither are they careful nor do they fear and protect [against wrongdoing], and nor are they to be trusted to not distort what you hear. They say what they know not when criticizing and decrying or when affirming their lies. But Allāh encompasses what they do. So be on guard against them, suspect them, reject them and distance yourselves from them, for this was what your earlier scholars and the righteous latter ones did and instructed others to do.

Beware of rising against Allāh and becoming instruments in the destruction of His religion and undoing its handholds by respecting the innovators, for you know what has come down to us about respecting them. And what stronger respect and veneration can there be than taking your religion from them, following them, believing them, being close to them and helping them in alluring those they allure and attracting those they attract of the weak Muslims towards their ideas and the religion they practice? This is enough to be considered a partnership and contribution to what they do.

Ibn ‘Asākir, Tārīkh Dimishq 6:361, 362.