Abu Dawood compiled twenty-one books related to Hadith and preferred those ahadith which were supported by the example of the companions of Muhammad. As for the contradictory ahadith, he states under the heading of 'Meat acquired by hunting for a pilgrim': "if there are two contradictory reports from the Prophet (SAW), an investigation should be made to establish what his companions have adopted". He wrote in his letter to the people of Mecca "I have disclosed wherever there was too much weakness in regard to any tradition in my collection. But if I happen to leave a Hadith without any comment, it should be considered as sound, albeit some of them are more authentic than others". Hadith Mursal (a tradition in which a companion is omitted and a successor narrates directly from Muhammad) has also been a matter of discussion among the traditionists. Abu Dawood states in his letter to the people of Mecca: "if a Musnad Hadith (uninterrupted tradition) is not contrary to a Mursal or a Musnad Hadith is not found, then the Mursal Hadith will be accepted though it would not be considered as strong as a Muttasil Hadith (uninterrupted chain)".