Imaam Al-Barbahaaree said, “However, if you see a person whose manner and opinion is despicable, he is wicked, sinful and oppressive, yet he is a person of the Sunnah, accompany him and sit with him, since his sin will not harm you. If you see a man who strives hard and long in worship, is abstemious, being continual in worship, except that he is a person of innovation, do not sit with him, do not listen to his words and do not walk along with him, since I do not feel safe that you will not eventually come to be pleased with his way and go to destruction along with him.”

(Sharh us-Sunnah, 149)