The following is posted from : Magnificent Points of Advice for those who have turned to the Way of the Salaf – Abu ‘Abdillaah Ahmad bin Muhammad Ash-Shihhee. This book was read to Allaamaah Rabee’ al-Madkhalee who gave some good instructions regarding it.
The Fourth Advice: Do not take Knowledge except from one who is known to be upon the Sunnah
Imaam Muhammad bin Sireen (rahimahullaah) said:
“Verily, this knowledge is Religion. So look into (i.e. investigate) whom you take your Religion from.”
And he said: “They (the Sahaabah) did not used to ask concerning the isnaad (chain of narration), but when the fitnah occurred, they began saying: ‘Name your men for us.’ So the People of the Sunnah would be looked to and so their hadeeth would be accepted. And the People of Innovation would be looked to and so their hadeeth would not be accepted.” 
So when one of these repentant individuals neglects these principles and guidelines, he becomes an open target for these misconceptions and he becomes a play object for many of those who (falsely) ascribe themselves to knowledge and Salafiyyah. So all it takes is for a person to claim knowledge or manifest his connection to the scholars from Ahlus-Sunnah, and you will find the repentant youth flocking around him, without thoroughly examining the reality of his condition and without looking into his history (i.e. background). But When he sees that his followers have become many and those who love him have become engrossed with him, he begins to reveal what he was concealing and what (way) he really inclined to. So now you see him calling to (holding) leadership in the field of Da’wah and pitching a tent for gathering everyone (i.e. regardless of beliefs). Or you see him doing other things that are in opposition to the principles of Ahlus-Sunnah wal Jamaa’ah.
This is the point where the repentant individuals begin to become confused and divided into two or even three categories – those who agree, those who are against and those who are neutral. This confusion only comes about due to two things:
First: The repentant individual’s lack of devoting attention to beneficial knowledge, especially knowledge of the Fundamentals of Ahlus-Sunnah wal Jamaa’ah, since Knowledge protects the one who has it from deviations.
Did you not see how knowledge protected Abu Bakrah (rady Alllaahu ‘anhu) in the Campaign of the Camel (Jamal), when the people put the Mother of the Believers, ‘Aa’ishah (rady Allaahu ‘anhaa) forth (for the campaign). So what protected Abu Bakrah (rady Allaahu anhu) was a hadeeth he heard from Allaah’s Messenger, who said when news reached him of the death of Kisraa and the appointment of his daughter (as the leader): “A people that leave their affairs to be governed by a woman will never prosper.”
So When the fitnah occurred, Abu Bakrah remembered this hadeeth and it protected him from that, such that he said: “Allaah protected me with something that I heard from the Messenger of Allaah When Kisraa died. He (sallAllaahu ‘alayhi wa sallam) said: Who did they put to succeed her?’ They said: ‘Her daughter.’ So he (sall Allaahu alayhi wa sallam) said: ‘A people that leave their affairs to be governed by a woman Will never prosper.’ So when ‘Aa’ishah approached, i.e. Basrah, I remembered the statement of Allaah’s Messenger and so Allaah protected me by it.” 
Second: A lack or returning to the People Of Knowledge, Since the most deserving to be asked are the People of Knowledge and their students from Ahlus-Sunnah wal- Jamaa’ah, those who have knowledge of this individual whom the people seek to study under. so this person Should be enquired into:
Is he from the Salafee students of knowledge or not?
And did he undergo valid educational studies, Such that he has the right to be sought knowledge from or no?
SO if the answer is in the negative, then the issue comes to an end, all praise be to Allaah. And if the answer is positive, then he can be Studied under and benefited from, but without going to extremes in that matter. Rather, he should be given his due place and status.
This is an important point, which is: Differentiating between the enlightened Scholars, those Who are referred to in issues related to knowledge and current events, such as the two Imaams, Muhammad Naasir-ud-Deen Al-Albaanee and ‘AbduI-‘Azeez bin ‘Abdillaah bin Baaz (rahimahumaAllaa) and those enlightened scholars Who remained after them, such as the Mashaayikh, Muhammad bin Saalih Al-‘Uthaymeen, Saalih bin Fawzaan Al-Fawzaan, Rabee’ bin Haadee Al-Madkhalee, our Shaikh, Muqbil bin Haadee Al-Waadi’ee and others who are at their level amongst the people Of knowledge and fatwaa from AhlusSunnah waI-Jamaa’ah. So these individuals have their own level and position…
And between the prominent students of knowledge, whose knowIedge is known and whose following of the Sunnah is apparent by way of their books and the commendations of the scholars for them. SO these individuals also have their own level and position…
And between those who are less than them, from the students of knowledge, Whose Salafiyyah is Known and Whose ability to teach is recognized.
 These last two narrations were reported by Imaam Muslim in his Introduction to his Saheeh
 Translator’s Note: The Campaign of the Camel occurred after the murder of Uthmaan, radyAlllaahu ‘anhu. when there was much turmoil amongst the Muslims. ‘Alee bin Abee Taalib radullaahu ‘anhu was given the bav’ah (oath of allegiance) as the succeeding Khaleefih and he decided to wait for the turmoil to simmer down before seeking revenge from the assassin of ‘Uthmaan. So the Muslims Were divided into those who were With him on this decision and those Who wanted justice for his murder right away. A group was formed to go and voice their case to ‘Alee and they rallied several of the Sahaabah including ‘Aa‘isha radhi Allaahu ‘anhaa‘ So she participated in the campaign riding on a camel (hence the name Jamal). When the parties at Basrah, a peaceful agreement was decided, yet due to some misunderstanding and confusion battle broke out and many lives were lost. And Allaah knows best.
 Reported by Al-Bukhaaree (7099), An-Nasaa‘ee (5403) and At-Tirmidhee (2365), and the wording mentioned here belongs to him.
Read the full e-Book: Magnificent Points of Advice for those who have turned to the Way of the Salaf – Abu ‘Abdillaah Ahmad bin Muhammad Ash-Shihhee