||R. David b. Abraham Oppenheimer (1664–1736), was born in Worms, his teachers were R. Gershon Ashkenazi of Metz, R. Jacob Ashkenazi, R. Benjamin Wolf Epstein of Friedberg, and R. Isaac Benjamin Wolf b. Eliezer Lipman of Landsberg. While he was still a boy, he maintained a scholarly correspondence with R. Jair Hayyim Bacharach. At the age of 17 he married Genendel, daughter of the Hanoverian Court Jew Leffman Behrends. A nephew of R. Samuel Oppenheimer, he inherited a fortune from him. At the age of 20 R. Oppenheim was ordained rabbi by his teachers in Metz and Landsberg, as well as by the rabbi of Worms, R. Aaron b. Moses Teomim. While his noble descent, his wealth, and the influence of his family may have helped him, as a scholar of repute he was entitled to recognition in his own right. When 25 he was called to the rabbinate of the highly respected community of Nikolsburg (Mikulov), thus becoming Landrabbiner of Moravia. There he gathered many students around him, founding a bet midrash which he endowed with large funds to ensure its continued existence for many years. In 1698 he received a call from the community of Brest-Litovsk and, although he declined, from this time he called himself rabbi of Brest. He also declined the call to become Landrabbiner of the Palatinate (1702). The community of Jerusalem honored him with the title "rabbi of the Holy City," which explains the use of the title "rabbi of Israel and of many communities and districts of the Diaspora" in the heading of his introduction to the Pentateuch (Berlin, 1705). Appointed nasi Erez Israel by R. Samson Wertheimer, R. Oppenheim became responsible for the collection and transference of sums collected throughout Europe for the benefit of Jews in Jerusalem. Many communities turned to him for help in regularizing their internal affairs; he prepared the statutes of the community of Hildesheim, which were partially accepted. After 12 years of successful activity in Nikolsburg, Oppenheim became rabbi of Prague, a community rich in talmudic scholarship. His munificence and liberality attracted many scholars. His wife Genendel died in 1712, and in her memory he donated a valuable Ark curtain to the Altneu synagogue. In 1713 he was appointed Landrabbiner of half of Bohemia, while the other half remained under the leadership of R. Benjamin Wolf Spira, whose daughter Shifrah, widow of R. Isaac b. Solomon Zalman Bondi of Prague, became R. Oppenheim's second wife. When R. Benjamin Wolf Spira died in 1715, he also became Landrabbiner of the other half of Bohemia.
Regarded as a man who was familiar with all branches of rabbinical and halakhic literature, R. Oppenheim also had a reputation as a mathematician, and many rabbis of the day turned to him with difficult questions of religious law. Many demands for his approbations (Haskamot) were made; Loewenstein has traced more than 70 of these. R. Oppenheim was reluctantly drawn into contemporary quarrels. Judah Leib Prossnitz vilified his name in an unprecedented manner - with his agreement, the rabbinate of Prossnitz (Prostejov) had excommunicated Judah Leib - but on the other hand he was accused by R. Zevi Ashkenazi of having given material and moral support to Nehemiah Hayon. It would appear that he had approved one of Hayon's works but that Hayon had printed the approbation in another. R. Oppenheim also had serious differences with R. Jonathan Eybeshuetz, who also worked in Prague. When R. Eybeshuetz's students slandered him in a most vulgar fashion, serious disturbances arose between the students of their respective yeshivot, prompting the authorities to intervene. In a decree of June 16, 1722, Emperor Charles VI ordered that the students responsible for the upheaval were not to remain in Prague and that "in future, Jewish studies be under the control of the said chief rabbi Oppenheim," and that no other Prague rabbi might maintain a house of study.
From his early youth a lover of books, R. Oppenheim undertook long journeys in order to obtain rare manuscripts or prints. He visited the fairs at Leipzig, was in close touch with printers and book dealers, and published lists of works he sought, in order to obtain books from all lands. He used his wealth (inherited and received from his wives) to establish a library. J. C. Wolf, who obtained most of the material for his Bibliotheca Hebraea from Oppenheim's library, estimated that it contained 7,000 volumes, including 1,000 manuscripts. An incomplete catalog of Oppenheim's library appeared in 1764, a second, by Israel Bresslau, was published in Hamburg in 1782, and a third, entitled Kohelet David, by Isaac Metz appeared in Hamburg/Altona in 1826 with a Latin translation by Lazarus Emden. A supplement to the latter was issued by J. Goldenthal in Leipzig in 1845. Because of censorship problems, the library was kept in Hanover; on R. Oppenheim's death it was inherited by his only son, R. Joseph, who married a daughter of R. Samson Wertheimer. After R. Joseph's death it passed to his nephew R. Isaac Seligman Cohen. One of Oppenheim's grandchildren, the widow of R. Hirsch Oppenheim of Hildesheim, put the library up for sale. M. Mendelssohn valued it at between 50 and 60,000 thaler, and it was later taxed for 150,000 thaler, but in 1829 it was finally sold for the ridiculously low sum of 9,000 thaler to Oxford, where it forms the substantial part of the Hebrew section of the Bodleian Library. R. Oppenheim was a patron of Jewish scholarship and gave many editors and publishers of talmudic and halakhic works grants toward publishing costs. He willingly put manuscripts that he had obtained at great expense at the disposal of publishers, in order to make them available to the wider public. Although R. Oppenheim himself wrote a great deal, the greatest part of his works lies unpublished in Oxford and other libraries. His responsa were published in the collections of responsa of R. Jair Hayyim Bacharach, R. Jacob b. Joseph Reicher-Backofen, R. Ezekiel Katzenellenbogen, R. Eliakim Goetz b. Meir, and R. Eliezer Lipschuetz.
Added t.p.: Catalogus der...Hebraeischen und Rabbinischen Bibliotheck...gesammelt von dem verstorbnen...Ober-Rabbin zu Prag David Oppenheimer, Herausgegeben von dem jezigen Besizzer...
Isaac Seeligmann Berend Salomon. Hamburg, gedruckt von Johann Michael Brauer