Abu Dawud Book 36, Hadith Number 5097.

Narated By AbuHurayrah : The Prophet (PBUH) said: Allah, Most High, has removed from you the pride of the pre-Islamic period and its boasting in ancestors. One is only a pious believer or a miserable sinner. You are sons of Adam, and Adam came from dust. Let the people cease to boast about their ancestors. They are merely fuel in Jahannam; or they will certainly be of less account with Allah than the beetle which rolls dung with its nose.