Sunan an-Nasa'i 4198

حَدَّثَنَا يَعْقُوبُ بْنُ إِبْرَاهِيمَ، قَالَ أَنْبَأَنَا عَبْدُ الرَّحْمَنِ، قَالَ حَدَّثَنَا سُفْيَانُ، عَنْ سُهَيْلِ بْنِ أَبِي صَالِحٍ، عَنْ عَطَاءِ بْنِ يَزِيدَ، عَنْ تَمِيمٍ الدَّارِيِّ، قَالَ قَالَ رَسُولُ اللَّهِ صلى الله عليه وسلم ‏"‏ إِنَّمَا الدِّينُ النَّصِيحَةُ ‏"‏ ‏.‏ قَالُوا لِمَنْ يَا رَسُولَ اللَّهِ قَالَ ‏"‏ لِلَّهِ وَلِكِتَابِهِ وَلِرَسُولِهِ وَلأَئِمَّةِ الْمُسْلِمِينَ وَعَامَّتِهِمْ ‏"‏ ‏.‏

It was narrated that Tamim Ad-Dari said:"The Messenger of Allah said: 'Religion is sincerity (An-Nasihah).' They said: 'To whom, O Messenger of Allah? He said: 'To Allah, to His Book, to His Messenger, to the imams of the Muslims and to their common folk

Reference

Sunan an-Nasa'i 4198

In-book

Book 39, Hadith 50