From Abu Nagih Al-Irbad Ibn Sariya, Allahs mercy on him:

The messenger of Allah, Allah´s mercy and peace be upon him, held an exhorting speech, by which the hearts were filled with fear and the eyes shed tears.

So we said: “Oh Messenger of Allah, this is like a farewell sermon. So advise us.”

He said: “I advise you to fear against Allah the mighty and exalted and to listen and obey, even if a servant is put in command over you.

Who of you who lives (long) will witness much dissension. So hold on to my sunna and the sunna of the rightly guided righteous successors. Bite on it with your teeth. Beware of new things (in belief) because ever new thing in belief is an innovation and every innovation is a wrong-going and every wrong-going leads to hellfire.” (Da, Ti)