That which seperates the people of truth and the people of falsehood is the Sunnah of the Messenger of Allaah (Sallallaahu 'Alayhi Wa Sallam). A jewel-filled section discussing topics such as 'The Saved Sect', Sticking to the Correct Manhaj In Times of Fitnah and 'Lessons In Manhaj'.
 

Al Haakim said: I heard ar-Rabee' [saying]: I heard ash-Shaafi'ee, and indeed he was narrating a hadeeth. So a man said to him: Will you implement this o Abaa Abdullaah? So he said: If I narrate an authentic hadeeth from the Messenger of Allaah (Sallallaahu 'Alayhi Wa Sallam) and I don't implement it, then you can testify that my intellect has left! [Reported by Ibn Abee Haatim in Aadaabush Shaafi'ee Wa Munaaqibuhu (p. 93), and by Imaam adh-Dhahabee in Mukhtasir Al Uloow' (no. 197) It's chain of narration is authentic. It was authenticated by Shaykh al-Albaanee in Sifatus Salaah (fifth edition) (p. 33)]

A man came to Imaam Maalik Ibn Anas (radiyallaahu 'anhu) and said: From where should I put on the ihraam? So he said: From the place where the Messenger of Allaah (Sallallaahu 'Alayhi Wa Sallam) stopped and put on ihraam. So the man said: So what if I put on ihraam from farther than that? So Maalik said: I do not advise that. So he said: What do you dislike about that? He said: I dislike the Fitnah upon you. He said: And what is the Fitnah in increasing the good?! So he said: Verily Allaah the Exalted says, "So let those who oppose his (Sallallaahu Alayhi Wa Sallam) command beware that a Fitnah may strike them, or a painful punishment." And which Fitnah is greater than you specifying an action with virtue which was not specified by the Messenger of Allaah (Sallallaahu 'Alayhi Wa Sallam)? [Related Abu Shaamah in his book Baa'ith 'alaa Inkaarul Bid'ah Wal Hawaadith (p. 14). Quoted by Abee Bakr Al Khallaal.]