Drawing on recent insights into textual authority, this article examines how the authoritativeness of the Jewish scriptures is manifested in 1 Clement. The article argues that the relationship between the letter and the writings it uses in its argumentation should be seen as a two-way process of mutual authorisation. Moreover, the article illuminates the interrelatedness of textual authority, scriptural argumentation and the legitimation of leadership and power. Thus, the analysis both contributes to ongoing scholarly discussions of scriptural authority and highlights the role of scriptural argumentation in the identity-building of early Christians.