There are numerous narrations from the salaf concerning how to deal with the innovators and warning against them. The salaf all agreed and were united upon this in every time and place, and this consensus has been conveyed by many of the people of knowledge. I will now state some examples:
On the authority of Abū Muzāhim Mūsâ ibn ʿ Ubaidullāh ibn Khāqān, who said: “My uncle, Abū ʿAlī ʿAbd al-Raḥmān ibn Yahyâ ibn Khāqān said to me: “al-Mutawakkil ordered Aḥmad ibn Ḥanbal to be asked who should take control of the judiciary. So I asked him.” Abū Mazāhim said: “So I asked him give me his answer, so he sent me a written copy. I returned to my uncle who confirmed the correctness of what I was sent, and this is what was written:
In the name of Allāh the Beneficent the Most Merciful, this is a copy of the note I presented to Aḥmad ibn Muḥammad ibn Ḥanbal, after I asked him concerning its contents and he answered me with that which I have written. He then ordered his son ʿAbdullāh to sign the bottom of it, by his order [alone] and I did not ask him to sign it.
I asked Aḥmad ibn Ḥanbal about Aḥmad ibn Rabāh, so he said about him: ‘Indeed he is a Jahmiyyah and is known for this, and if he is made responsible for the judgment of Muslim affairs, he will cause harm to them due to the methodology and innovations he is upon.’
Then I asked about Ibn al-Khalnajī, so replied about him the same thing he said concerning Aḥmad ibn Rabāh and mentioned that he is a known Jaḥmī, and he was from the most evil and harmful of them to the people.
Then I asked him about Shuʿaib ibn Sahl, and he said about him: ‘He is a known Jahmī.’
So I asked him about “ʿUbaidullah ibn Aḥmad, so he said about him: ‘He is a known Jahmī.’
So I asked him about the one known as Abī Shuʿaib, so he said: ‘Indeed he is a known Jahmī.’
Then I asked him about Muḥammed ibn Mansūr, the Judge of al-Ahwāz. He said: ‘Indeed he was with Ibn Abī Dāwūd, he was upon his view and his deeds, except that he was one of the best of them, but I do not know what opinion he holds.’
Then I asked him about ʿAlī ibn al-Jʿād, he said: ‘He was known among the people to be a Jahmī and was famous for it, then it reached me that he renounced that.’
Then I asked him about al-Fath ibn Sahl the one responsible for the acts of injustice against Muḥammed ibn Abdullāh in Baghdad, so replied said: ‘He is a known Jahmī from the companions for Bishr al-Mirīsī and it is not befitting for anyone to place the likes of him in charge of anything from the affairs of the Muslim because of harm it entails.’
So I asked him about Ibn al-Thaljī, so he said: ‘He is an innovator and a person of desires.’
So I asked him about Ibrahīm ibn Uʿtāb, he said: ‘I do not know anything about him except he was from the companions of Bishr al-Mirīsī.”
Therefore it is befitting to be wary of him and not to get close to him. He should not be put in charge of any affairs of the Muslim.’
In short, the aid of the people of innovation and the people of desires are not to be sought in any of the Muslim affairs, because this is one of the greatest harms to the religion in spite of the opinion of the commander of the Believers, may Allāh ﷻ cause his firm stance upon the sunnah and opposition to the innovators remain.”