Arba'un 7 — the religion is sincerity

الأربعون 7 — الدين النصيحة

Tamim al-Dari's hadith, the seventh of al-Nawawi's Forty and of Ibn Rajab's commentary; transmitted by Muslim (55) through Suhayl ibn Abi Salih from Ata ibn Yazid al-Laythi from Tamim al-Dari, and also reported from Abu Hurayra, Ibn Umar, Thawban and Ibn Abbas, al-Bukhari holding the whole hadith to rest on Tamim; Ibn Rajab cites Abu Dawud that it is one of the hadiths around which jurisprudence revolves, and Muhammad ibn Aslam al-Tusi that it is a quarter of the religion, and gathers al-Khattabi's and Ibn al-Salah's definitions of nasiha and the texts on sincerity to Muslims and to those in authority (Jami' al-Ulum wal-Hikam pp. 193–204).