The first contacts between Mostapha Naji and Leiden scholars of Islam and Arabic date from the late 1980s. In 1988 Nico Kaptein, currently University Lecturer of Islam at Leiden University, introduced Mostapha Naji to Léon Buskens, currently Professor of Islamic Law at the same university. Not long afterwards, the first purchase of a manuscript by Leiden University Library was registered in March 1990 (Or. 22.315). Between 1990 and 2000 Jan Just Witkam, Curator of Oriental Manuscripts at Leiden University Library, bought manuscripts and lithographed editions from Mostapha Naji on a regular basis, largely with the mediation of Buskens. After Naji’s death in 2000, his two sons were unable to continue the book business. Nevertheless, acquisition continued on a more modest scale, mostly from private owners who had previously bought manuscripts from Naji, such as Belkacem Aït Salah Semlali (Rabat), P.S. van Koningsveld (Leiden), more recently from Léon Buskens (Leiden), and from Mostapha Naji’s heirs. In 2010, for instance, the remainder of Naji’s manuscripts, scholarly notes and some lithographed books were added to the collections with the financial support of the Juynboll Stichting, Leiden.

In 2012, Naji’s extensive reference library was acquired by LUCIS, the Leiden University Centre for Islamic Studies and subsequently donated to Leiden University Library.

In several cases substantial grants for the purchase of manuscript and book materials have been awarded by charities such as the Juynboll Stichting, VSB Fonds (The Hague) and Stichting het Oosters Instituut (Leiden).