Hadith #7 (The Forty Hadith of Imam Nawawi)
Book: Religion is sincere advice (nasihah)
Narrator(s): Tameem ibn Aus ad-Daree
Grade: Sahih

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.”

Source: https://parallelquran.com/hadith/forty-nawawi-7/