In this narration, the Prophet(pbuh) clearly told to Sa'ad bin Abbi Waqas that there is a difference between a Muslim and faithful true believer (momin).
This narration also show another interesting thing, The Prophet said I love more a person than the other, but whom I love, I give him less and the other person gets more from me because I have fear that person might go to hell fire,( that's why I give more to the second person to keep him in the group of Muslims).
Please read The Holy Quran (49:14)
"The bedouins say, "We have believed." Say, "You have not [yet] believed; but say [instead], 'We have submitted,' for faith has not yet entered your hearts. And if you obey Allah and His Messenger, He will not deprive you from your deeds of anything. Indeed, Allah is Forgiving and Merciful."
The verse of The Holy Quran and the narration of Sahih Muslim invalidates the theory of those fellows who claim all the companions are righteous and عادل a'adil, follow anyone you will be guided.
Please read Shia-Sunni point of view about the Companions of the Prophet on the main page.
http://sunnah.com/muslim/1/285
