Imam Abu Dawud lived a couple of centuries after the Prophet Muhammad (P.B.U.H) passed away and worked extremely hard to collect his ahadith. Each report in his collection was checked for compatibility with the Qur’an, and the veracity of the chain of reporters had to be painstakingly established.
Abu-Dawud’s collection is recognised by the overwhelming majority of the Muslim world to be one of the most authentic collections of the Sunnah of the Prophet (P.B.U.H), however, it is also known to contain some weak ahadith (some of which he pointed out, others which he did not).
Though Abu Dawud collected 50,000 Ahadith, he compiled only 4,800 in his book entitled As-Sunan, which he used to teach in Baghdad and other major cities in his time. He died in Basra on Friday in the month of Shawwal 275 AH. Sunan Abu Dawud has been translated into English.