The composition of traditional Arabic texts is a complex problem. The field has produced a number of studies where excerpts of excessively long texts are analyzed in the most meticulous manner. Unfortunately, since the studied samples are usually short, we can hardly hope to gain a deep understanding of the writing practices of Arab authors. Relying on computer-based algorithms, the paper argues that we can surpass this limitation and start evaluating massive Arabic texts in their entirety and understand patterns of text reuse at the level of specific books as well as at the level of specific authors, i.e. analyzing all of their available works. Taking this approach further, we can use the generated text-reuse data to identify parts of a text that a given author 1) borrows verbatim; 2) omits from his sources; and 3) supplements (or modifies) with his own information. The resultant aggregations of text bits can then be analyzed with different clustering techniques in order to identify patterns in borrowings, amendments, and omissions which should lead to a better understanding of authorial practices. The paper will present the inner workings of the proposed method and will focus on one of the major historical texts written during the Mamluk period of Islamic history—“Ta?rikh al-islam” of al-Dhahabi (d. 1348). In the section on the biography of the Prophet, al-Dhahabi draws on extensively on materials from “Sirat al-Nabi” by Ibn Hisham, “al-Tabaqat al-Kubra” by Ibn Sa?d, “Ta?rikh” by al-Tabari, and particularly “Dala?il al-Nubuwwa” by al-Bayhaqi. Current analysis of text-reuse patterns strongly suggests that al-Dhahabi is genuinely trying to preserve information from his sources, mostly quoting them verbatim; at the same time he does modify reused text, but largely in a non-destructive manner (most commonly, al-Dhahabi drops repetitions of long names or replaces them with pronouns). The paper will present the most recent findings in al-Dhahabi’s text reuse patterns; in order to get a more robust perspective on al-Dhahabi’s text reuse patterns for the Prophetic materials, they will be presented in comparison with al-Dhahabi’s text reuse from Andalusian sources.