مُسْنَدُ أَحْمَدَ
Musnad Ahmad 3258
Musnad of 'Abdullah bin al-'Abbas bin 'Abdul-Muttalib from the Prophet
Abdur-Rahman bin Thawban said: I heard 'Amr bin Deenar say: Someone who heard Ibn ‘Abbas (رضي الله عنه) told me that he said: The Messenger of Allah (ﷺ) said: "Religion is sincerity (naseehah)." We said: To whom? He said: “To Allah, to His Messenger and to the leaders of the believers.”
Musnad Ahmad 3281Saheeh because of corroborating evidence; this is a da’eef i