Deen e Islam is naseehah (Advice sincerity) Hadith narrated by Saheeh Muslim

Hadeeth 7  (From 40 Hadith collection of Imam Nawwi Related by Muslim.)
On the authority of Tameem ibn Aus ad-Daree (may Allah be pleased with him):

The Prophet (peace and blessings of Allah be upon him) said,
 “The deen (religion) is naseehah (advice, sincerity).” 

We said “To whom?” 

He (peace and blessings of Allah be upon him) said

 “To Allah, His Book, His Messenger, and to the leaders of the Muslims and their common folk.”

Related by Muslim.