Imaam Ibn Rajab (rahimahullaah) said:

He (sallal-laahu – alayhi – wasallam) commanded that during splitting and differing, one should adhere to his Sunnah and the Sunnah of the rightly guided khulafaa after him. The Sunnah is the path that is adhered to, and that includes adhering to what he (sallal-laahu-alayhi wasallam) and his rightly guided khulafaa were upon with regards to creed, actions and statements.  This is the complete Sunnah.  [Jaami-ul uloom wal hikam page:249]