The Damascus Document (CD) (the Cairo Damascus document) or Damascus Rule is one of the most interesting texts of the Dead Sea Scrolls because it is the only Qumran sectarian work that was known before the discovery of the Dead Sea Scrolls.
There were a number of fragments from the scroll found in the Cairo Geniza before the Qumran discoveries. The Cairo Geniza was located in a room adjoining The Ben Ezra Synagogue in Old Cairo, which was gradually stuffed full of papers until it was discovered by European scholar Dr Solomon Schechter in 1897. He found over 190,000 manuscripts and fragments that were written in mainly Hebrew and Judaeo-Arabic. 
The fragments were quite large, and a number of them matched documents found later in Qumran. They were divided into two separate sections, CDa, and CDb. Schechter dated CDa to the 10th century C.E and CDb to 11th or 12th century C.E.  In contrast to the fragments found at Qumran, the CD documents are largely complete, and therefore are vital for reconstructing the text.
The title of the document comes from numerous references within it to Damascus. The way this Damascus is treated in the document makes it possible that it was not a literal reference to Damascus in Syria, but to be understood either geographically for Babylon or Qumran itself. If symbolic, it is probably taking up the Biblical language found in
, “therefore I shall take you into exile beyond Damascus”; Damascus was part of Israel under King David, and the Damascus Document expresses an eschatalogical hope of the restoration of a Davidic monarchy.
The combined text of CDa and CDb contains twenty columns of writing. As it has come down to us, two columns have been mislocated: columns 15 & 16 originally preceded
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. Fragments of this text from Qumran include material not found in CD. The document divides into two parts, commonly called Admonition and Laws. Davies divides the Admonition into four sections: History, Legal, Warnings, a Supplement (which Wise refers to as exhortations). The Laws feature Oaths & vows, Sundry rulings (halakhot), Camp laws, and a fragment of Penal codes (more of which were found in the Qumran fragments).
The Damascus Document can be divided into two separate sections of work, The Admonition and the Laws. The Admonition comprises moral instruction, exhortation, and warning addressed to members of the sect, together with polemic against its opponents; it serves as a kind of introduction to the second section. Meanwhile, the Laws looks at this new covenant community expressed to them through the Teacher of Righteousness. It goes into great detail of the different social arrangements that were taking place at the time. 
This part is divided into four subsections that each outline different parts of information that were especially relevant to the new covenant community.
Section I, 1-V, 12a there is a strong description of the community and how they originated with their purpose and goals. Section IV, 12b-VII,9 it outlines the views of people in and outside the community, and discusses that these people are straying from the real law. Meanwhile the people in this community are drawn together by the covenant, and strict laws they follow together. It is said that people who follow this law will attain salvation. Section VII, 5-VIII, 19 outlines the strong warnings given to the people who stray from the law, and gives vivid critiques of the Prince of Judah, and also three nets of Belial. Section XIX, 33-XX,34 has more warnings of not betraying the community, and making promises to be faithful. 
A. Admonition (1-8 + 19-20)
The Laws The first 12 laws are from the Damascus Document found at Qumran, while the others are from Cairo Geniza. 1. Introduction the new laws, priests, and overseer. 2. Rules about priests and disqualification 3. Diagnosis of Skin disease 4. Impurity from menstruation and childbirth. 5. Levitical laws pertaining to harvest. 6. Gleanings from grapes and olives 7. Fruits of the fourth year. 8. Measures and Tithes 9. Impurity of Idolators metal, corpse impurity, and sprinkling. 10. Wife suspected of adultery 11. Integrity with commercial dealings and marriage 12. Overseer of the camp 13. 15.1-15a: Oath to return to the law of Moses be those joining the covenant 14. 15.15b-20: Exclusion from the community on the basis of a physical defect. 15. 16.1-20: Oath to enter the community, as well as laws concerning the taking of other oaths and vows. 16. 9.1: Death to the one responsible for the death of a Jew using gentile courts of justice. 17. 9.2-8: Laws about reproof and vengeance 18. 9.9-10.10a: Laws about oaths, lost articles and testimony and judges. 19. 10.10b-13 Purification in water. 20. 10.14-11.18 Regulations for keeping the Sabbath 21. 11.19-12.2a Laws for keeping the purity of the Temple. 22. 12.2b-6a Dealing with transgressors 23. 12.6b-11a Relations with gentiles 24. 12.11b-15a Dietary laws 25. 12.15b-22a Two purity rules 26. 12.22b-14.19 Regulations for those in the camps 27. 14.20-22 Penal code dealing with infractions of communal discipline 28. Expulsion ceremony. This was found in Qumran.
B. Laws (15-16 + 9-14)
The document contains a reference to a cryptic figure called the Teacher of Righteousness, whom some of the Qumran scrolls treat as a figure from their past, and others treat as a figure in their present, and others still as a figure of the future. This Teacher of Righteousness features prominently in the Damascus Document, but not at all in the Community Rule, another document found amongst the Qumran scrolls, suggesting a difference in the situation during the writing of each. One of the major reasons this person is so significant is because he also appears in a number of other texts from the Dead Sea Scrolls. Some of these other scrolls where he is mentioned are the Habakkuk Pesher (numerous times), Micah Pesher (once), Psalms Pesher and also 4Q172. The most interesting scroll is one where he is not mentioned, that being the Rule of the Community. He is first introduced in the Damascus Document by discussing the 390 years after the fall of Jerusalem: “And God observed their deeds, that they sought Him with a whole heart, and He raised for them a Teacher of Righteousness to guide them in the way of His heart.” Scholars have believed that he was a priest, and leader of this covenant community. There are other variations in the text that are also thought to be him. These include: “the teacher”, “the unique teacher” and “the interpreter of the law. The Damascus Document describes the group amongst whom the Document was created as having been leaderless for 20 years before the Teacher of Righteousnessestablished his rule over the group. Usually historians date the Teacher to circa 150 BCE, since the document states that he arrived 390 years (a period which, however, is unlikely to be precise) after the Babylonian Exile.
There is a high degree of shared terminology and legal rulings between the Damascus Document and the Community Rule, including terms like sons of light, and their penal codes. The fragment 4Q265 appears to have come from a hybrid edition of both documents.
The textual relationship between the Damascus Document and Community Rule is not completely resolved, though there is a general agreement that they have some evolutionary connection. Some suspect that the Community Rule is the original text that was later altered to become the Damascus Document, others that the Damascus Document was redacted to become the Community Rule, a third group argues that the Community Rule was created as a utopian ideal rather than a practical replacement for the Damascus Document, and still others that believe the Community Rule and Damascus Document were written for different types of communities, one enclosed and the other open.