«Al-Luma' fi Usul al-Fiqh» is a book on the principles of jurisprudence according to the Shafi'i school of thought. Its author was Abu Ishaq al-Shirazi. Some of his brothers asked him to compile a summary of the principles of the school of thought for them, so he responded to their request and wrote this book. The author summarized his book «Al-Tabsira fi Usul al-Fiqh». Its author said: «Some of my brothers asked me to compile a summary of the school of thought, on the principles of jurisprudence, so that it would be added to what I did in Al-Tabsira, on the differences, so I responded to him to that in response to his question and to fulfill his right, and I indicated in it the mention of the differences and what is necessary from the evidence, so that it may fall to someone who does not have what I did from the differences.» He began compiling it in the year 455 AH and finished it in the year 469 AH. The book includes a lot of evidence. Shafi'i jurists were interested in it, so the author himself explained it, as did Diya' al-Din al-Kurdi, and Abu Muhammad Abdullah bin Ahmad al-Baghdadi.