This study focuses on how, over centuries, discarded Hebrew documents generally have been reused. By examining forms, languages and methods for new research, we intend to offer a picture of this phenomenon, highlighting various characteristics, typical of the reuse of documents from the Jewish world. Unlike Christians, for Jews, documents that were deteriorated could by no means be reused, since they might contain the name of God, which would be profaned by any possible reuse. Since ancient times, the sacredness of the name of God has created the practice of placing all out-of-use sacred documents and texts, manuscript or printed, in a genizah (read ghenizàh), as a transitional phase to their burial. The genizah constitutes neither a library nor an archive that could be consulted. Of particular interest is the reuse of the sheets of two loan registers in paper, where two Jewish bankers, active in Bologna in the early fifteenth century, recorded their loans or some Ketubbot, i.e. beautifully illustrated marriage certificates in parchment, reused as book covers, one of which ended up in New York, together with the book it was used for as a cover. A parchment document drawn up in Mantua and dated 1517, discovered in a binding at the State Archives of Modena contains the rental deed of a loan bank, stipulated by widowed Stella Norsa, following her husband’s death. Many other cases could be cited, well aware of the enormous quantity of Hebrew documents still undiscovered or undocumented in Italian archives and libraries, as well as those in Europe and other continents.