Tradition, as above described, is not confined to details belonging to the
  lifetime of Mahomet. The childish habit was contracted of putting the relation
  of every trivial fact and story into the popular form of a tradition with its
  string of authorities; and there is consequently a great mass of
  quasi-traditional matter on the early progress of Islam subsequent to the
  Prophet's death. Excluding this, and confining our view solely to what belongs
  to the lifetime of Mahomet, it is remarkable that the original sources, the
  recognised "Sheikhs" or Fathers of tradition, are comparatively few,
  great numbers having been rejected by the Collectors as inadmissible. . Thus
  Hâshid (d. 258) relates that he had heard the recitals of 1750 Sheikhs, but
  adopted in his collection the traditions of but 310; he had collected separate
  traditions to the number of one million and a half, but accepted only 300,000.
  Wâckidi, again, amassed probably a couple of millions, but the number of
  Sheikhs he relied on was small. Setting aside repetitions of the same
  occurrence, he retained in his collection not more than some 40,000
  traditions, of which perhaps not half are genuine; and even of these, many
  relate to one and the same subject-matter.