Mustadrak al-Hakim — Hadith 333

It is narrated from Sayyiduna al-Irbad bin Sariyah (may Allah be pleased with him) that the Messenger of Allah (peace and blessings be upon him) led us in the morning (Fajr) prayer, then turned his blessed face towards us and gave us such a moving admonition that hearts trembled and eyes shed tears. We said: O Messenger of Allah! It seems as though this is the admonition of one bidding farewell, so give us some counsel. He (peace and blessings be upon him) said: "I counsel you to fear Allah, and to listen and obey (the ruler), even if a slave is made your leader; for whoever of you lives (after me) will see much disagreement. So hold fast to my Sunnah and the Sunnah of the rightly guided caliphs (al-Khulafa' al-Rashidun); bite onto it with your molar teeth, and beware of newly invented matters (in the religion), for every innovation is misguidance."
This hadith is sahih (authentic) and there is no hidden defect ('illah) in it. Imam Bukhari used Abd al-Rahman bin Amr and Thawr bin Yazid as evidence, and mentioned this hadith at the beginning of his Book of Holding Fast to the Sunnah. In my view, both of them (Imams Bukhari and Muslim) were under the impression that no one besides Thawr bin Yazid narrated from Khalid bin Ma'dan, whereas Muhammad bin Ibrahim bin al-Harith, whose hadith is found in the two Sahihs, also narrated it from Khalid bin Ma'dan.