The saved group is the people who believed in Allah and followed His Apostle,
and worked according to his will and adhered to it. You already knew that the
Prophet (P.b.u.h) warned from sedition, disagreement, going astray, and
returning to the state of ignorance. Therefore he gave people the safety and
guided them to the life boat, and recommended them to ride it in his will before
his death. This will was the safety that keeps people away from sedition,
disagreement, going astray in condition of believing in this will and working
according to it. Then a human will keep along with Islam and its method, and he
will be away of deviation.
So, the saved group is the one which followed the saying of the Prophet
(P.b.u.h), and his progeny (P.b.u.h) and worked according to his will.