Harun bin Ishaq bin Muhammad هارون بن إسحاق بن محمد بن مالك · The Book of al-Bay'ah

"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"'