Shaykh Zayd Al-Madkhalee said, “An innovator is observed, the principle regarding someone who innovates in Allah’s religion is that he is advised by the people of knowledge to give up his innovation.
If he gives up his innovation, then he is a noble brother and knowledge is taken from him and he is loved for the sake of Allaah.
But if he continues upon his innovation, he is forsaken, the Muslims abandon him [boycotted] and they [the people of knowledge] warn the people against him.
So there can be no consideration nor respect for him because he introduced an innovation that is not from the religion into the religion Allaah. In this respect he is like a legislator, as if he is making laws along with Allaah and this shows the danger of innovation in the religion. It is the same whether this [innovation] is in aqeedah (creed) or in other than it from amongst the practised methodology.
Knowledge is not taken from him except if some knowledge is found with him that has no connection with his [specific] innovation and the people need it [that knowledge] from him [as they can not access that knowledge from anyone else from the people of knowledge upon the Sunnah for whatever reason].
[But] they should not keep returning to him or make people believe that he is from amongst the scholars [upon the Sunnah] or those close to Allaah.
Rather, they make his affair clear to the people.
How do we know about the innovators since the time of the companions [of the Prophet] to our present time? We know a large amount of them through what was written about them, those amongst them who were notorious for innovation.
So the Khawaarij [those who rebel against the sinful Muslim ruler and declare Muslims as disbelievers for major sins] became notorious and the Rawaafidh [the exterme Shia] became notorious and the Mu’tazilah [those who hold a major sinner is neither a Muslim or a disbeliver in this world and in the hereafter he will be in hell forever] and the Jahmiyyah [who are] deniers of [all of] Allaah’s attributes and the Hulooliyyah [believers in Allaah’s presence inside certain people from the creation] and the Ittihaadiyyah [believers in Allaah’s unity with his creation meaning they hold Allah is inside every created thing inanimate and animate] and various innovations and their leaders – we know about them through what the champions out of the scholars [upon the Sunnah], [those] people of good faith, truth, and sincerity, wrote about them.
So their [the innovator’s] affair became clear and their perverted beliefs became known and whoever Allaah had decreed to be from the saved and aided sect, Ahlu Sunnah Wal Jamaah avoided them [those deviant beliefs]. Whoever pays no attention to this and does not care, then he has wronged himself.
So the point is that we warn…against the people of innovation and whatever knowledge we want to seek then we should ask the people about the people of Sunnah and we should take knowledge from them and we should take are chain of narration from them, so that none of our sources (in the chain) are from the people of innovation. Because the people of Sunnah forsake the innovator both dead and alive. They clarify his innovation while he is alive and they [continue to] clarify his innovation when he is dead and they consider that to be part of the actions that bring them closer to Allaah and that is the truth.”
Ref: dusunnah.com with slight adaptation by ahlusunnahwaljamaah.com for easier understanding
Posted by Abdul Kareem Ibn Ozzie