Riyad as-Salihin (Nawawi's Forty) · Hadith 7
عن ابي رقية تميم بن اوس الداري رضي الله عنه ان النبي صلى الله عليه وسلم قال: "الدين النصيحة." قلنا: لمن؟ قال: "لله، ولكتابه، ولرسوله، ولايمة المسلمين وعامتهم." [رواه مسلم]
On the authority of Tameem ibn Aus ad-Daree (ra): The Prophet (ﷺ) said, “The deen (religion) is naseehah (advice, sincerity).” We said, “To whom?” He (ﷺ) said, “To Allah, His Book, His Messenger, and to the leaders of the Muslims and their common folk.” [Muslim]