Sunan Ibn Majah, Chapter: The Book of the Sunnah

that the Messenger of Allah (saw) said: "May Allah cause his face to shine, the man who heard what I say and conveys it (to others). There are those who have knowledge but no understanding, and there may be those who convey knowledge to those who have more understanding of it than they do." (One of the narrators) Ali bin Muhammad added to it: "There are three things because of which hatred does not enter the heart of a Muslim: Sincerity in doing an action for the sake of Allah; being sincere towards the rulers of the Muslims; and adhering to the Jamaah (main body) of the Muslims." (Hasan)