Al-Sarakhsi

Muhammad b. Ahmad b. Abi Sahl Abu Bakr al-Sarakhsi () was a Persian jurist, or Islamic scholar of the Hanafi school. He was traditionally known as Shams al-A'imma (, "the sun of the leaders").
He is an influential jurist in the Hanafi school where the tradition is reported to have been that: "when in doubt, follow Sarakhsi". Both Al-Kasani and Burhan al-Din al-Marghinani, in their flagship fiqh books of "Bada'i' al-Sana'i"' and "Al-Hidaya", have extensively drawn upon the discussions and legal reasonings presented in al-Sarakhsi's "Al-Mabsut" and "Usul al-Sarakhsi".
The Indian Muslim scholar of the 19th century, Abd al-Hayy al-Lucknawi, classifies al-Sarakhsi in the second grade of "mujtahids", along with scholars such as Al-Tahawi, who are believed to be the seminal jurists after Abu Hanifa's students (i.e. Abu Yusuf and Muhammad al-Shaybani).
Background Information.
Al-Sarakhsi was born in Sarakhs, a city in Greater Khorasan, which is presently located at the border between Iran and Turkmenistan. He died in 483/1090 or in 490/1096, according to different sources.
He studied under the great Hanafi jurist, 'Abd al-'Aziz al-Halwani (d. 448/1056) who was also a teacher to Al-Bazdawi.
Not much is known about his early life, though some clues are found in his works. It is said that al-Sarakhsi was imprisoned due to his opinion on a juristic matter concerning a ruler; he criticized the king by questioning the validity of his marriage to a slave woman. He spent around fifteen years in prison. While he was imprisoned he wrote the "Mabsut" and some of his other most important works. He is known for his remarkable memory, (he was able to recall many texts when he was held in prison) as well as his intelligence.
Al-Sarakhsi's opinions on law have been widely cited and he has been thought of as a distinctive writer. His main works are the "Usul al-Fiqh", "the Kitab al-Mabsut", and the "Sharh al-Siyar al-Kabir".
Important Works.
Al-Sarakhsi's most important works are 
Usul al-Fiqh.
This work deals with Islamic jurisprudence and the exercise of ra’y in systematic reasoning and juristic preference. To write this work, al-Sarakhsi incorporated information from many different sources, including Abu’l-Hasan al-Karkhi, Ahmad b. Muhammad al-Shashi, al-Djassas, Abū ʿAbdullāh Muhammad ibn Idrīs al-Shafiʿī and major works from the other law traditions.
Kitab al-Mabsut.
Al-Sarakhsi's "Mabsut" is a commentary on the "mukhtasar" (epitome) by Muhammad b. Muhammad al-Marwazi, which in turn summarized some of the foundational texts of the Hanafi school written by Muhammad al-Shaybani. Al-Shaybani was a companion of Abū Ḥanīfah, the founder of the Hanafi school. In his "Mabsut", Al-Sarakhsi reworks many of the concepts from al-Shaybani's works. He organized his work around points of dispute (ikhtilaf) and incorporated more information from the Hanafi school, as well as other schools of law. The "Mabsut" is well-organized, covers topics comprehensively, explores points of dispute thoroughly, and manipulates hermeneutical argument well. These factors make the "Mabsut" a very influential piece of juristic literature; it was an important work of "furu" (the elaboration of rulings based on the Principles of Islamic jurisprudence) in the Hanafi school until the 19th century. "Its significance in later times is reflected in the statement of the 15th-century Hanafi jurist, 'Ala' al-Din al-Tarabulusi (d. 1440): 'Whoever memorizes "al-Mabsut" and the doctrine of the ancient scholars becomes thereby a mujtahid.'" Al-Sarakhsi deals with many themes in his "Mabsut", these include juristic preference, the legality of doing activities with illegally obtained objects, zakat (alms tax, one of the Five Pillars of Islam) and land reclamation. 
In the "Mabsut" he defines the doctrine of istihasn, or juristic preference, as the "abandonment of the opinion to which reasoning by the doctrine of ...systematic reasoning would lead, in favor of a different opinion support by stronger evidence and adapted to what is accommodating to the people. Thereby, Sarakhsi neither undermines the importance of the exercise of the doctrine of systematic reasoning nor rejects it in any sense." In addition, al-Sarakhsi deals with the dilemma of doing a legal activity with an illegally obtained object. The fact that the object was obtained illegally does not mean that the legal activity becomes illegal. Al-Sarakhsi also deals with issues concerning zakat in the "Mabsut". For example, if the collector comes and a person denies that something is taxable, he does not have to pay the tax on that item, since it is a duty to God. This is explained in the following passage from the Mabsut, which is quoted in Classical Islam: A Sourcebook of Religious Literature, by Norman Calder, Jawid Ahmad Mojaddedi, and Andrew Rippin:
 Al-Sarakhsi also mentions the views of Abu Hanifa on land reclamation. This passage is from al-Sarakhsi's "Mabsut", as quoted by Sherman A. Jackson:
Sharh al-Siyar al-Kabir.
This work is a commentary on the "Kitab al-Siyar al-kabir" of al-Shaybani. It demonstrates the role of juristic preference in sharia law. The "Sharh al-Siyar al-Kabir" shows the same widespread coverage, the development of rules and careful consideration of hermeneutical argument that is seen in the "Mabsut".