In the late ancient Mediterranean, biblical commentary often took citational form through the creation of catenae. The citational gesture of such projects deployed the authority of tradition and embedded the biblical lemma within an interpretative frame. Late ancient catenae for Matthew, Luke, John, and other biblical texts reconfigured prior commentary. Yet because Mark lacked a commentary tradition, one could not use existing commentaries on Mark to construct a catena. The absence prompted an innovative form of recycling: the sixth-century Catena in Marcum repurposed commentary on Matthew, Luke, and John in order to create a novel catena for Mark. T his double act of recycling reappropriated existing commentary for a new text. The resulting catena embedded Mark within a fourfold tradition of gospel commentary, underscoring narrative and theological tensions between Mark and other gospels. Since similar tensions and ruptures attend other commentarial projects as well, the Catena in Marcum illuminates the broader practice of recycling in commentary.