IMAM ABU DAWOOD
Imam Abu Dawud (full name Abu-Dawud Sulaiman bin Al-Aash'ath Al-Azdi as-Sijistani) was born in 202 A.H in Sajistan, a place near Qandhar in Afghanistan. He was one of the most widely travelled of the scholars of ahadith, going to Saudi Arabia, Iraq, Tarsus, Damascus, Khurasahn, Egypt, Basra, Syria, Nishapur, Marv, and other places for the sole purpose of collecting ahadith. His primary interest was in law (fiqh), hence his collection focuses purely on legal ahadith.
Imam Abu Dawud began the learning of hadith while he was less than 20 years old. He gained a wide reputation in his lifetime. The scholars are unanimous about his great ability, trustworthiness and accuracy. He was not only a good narrator of hadith but also a good lawyer. Sometimes he checked written material, papers, and ink to discover their age. 
His most famous of all his works is Sunan Abu Dawud. It contains 4800 traditions which were taken out from a collection of 500,000 hadith, based on their superior authenticity. Total sunan is divided into 43 books.
He completed its compilation at Bagdad in 241 A.H. He presented the completed compilation to his beloved teacher Imam Ahmad ibn Hanbal who was greatly pleased at this collection.
Sunan Abu Dawud is an important collection of hadith: Most of the scholars have assigned it to third position among the six authentic books of hadith. It is only after the compilation of Sahih Bukhari and Sahih Muslim. 
A few statements from scholars of hadith concerning Sunan Abu Dawud:
Al-Khattabi said: Sunan Abu Dawud is an excellent book. No such parallel work has been produced so far in religious sciences. It has gained popularity amongst the people. It has a decisive position among various classes of scholars and jurists. All have benefited equally from it. The people of Iraq, Eygpt, Maghrib and most of the countries depended upon it.
Ibn al-Jawzi said: Abu Dawud was an eminent doctor of hadith and an outstanding scholar. No one has compiled a book like his Sunan.
Ibn Kathir remarked: Sunan Abu Dawud is considered to be a famous and popular work among scholars. 
Imam Abu Dawud heard hadith from 300 persons who were his teachers. Some were: Imam Ahmad ibn Hanbal, Ishaq ibn Rahawaiy, Abu Thaur, Yahya ibn Ma'in. For one to grasp his elevated status, he narrated hadith to the teachers of Imam Ahmad. Imam Ahmad ibn Hanbal also narrated one hadith from him.
Among the students of Imam Abu Dawud are great personalities like: Ibn Arabi, Abu`Isa al-Tirmidhi and Abu `Abdur-Rahman An Nasa'i. They were transmitters of his famous work Sunan Abu Dawud. 
Many commentaries have been written on the book, the best is Shamsul Haq Azimabadis Awn al Mabud Sharh Sunan Abi Dawud. 
Imam Abu Dawud died in 275 A.H. at the age of 73. (To Allah we belong and to Him we shall return).