Although previous studies of the kharaj have acknowledged that its theoretical contours changed during the early centuries of Islam, these studies have lacked access to sources that would enable them to track these changes in detail. In this paper, I fill this gap in the conceptual history of the kharaj by making use of sources from the second and third hijri centuries. These sources fall into two main categories. The first consists of normative sources of tafsir, fiqh, and hadith such the Kitab al-jihad of Ibn al-Mubarak (d. 181), the Musannaf of 'Abd al-Razzaq al-San’ani (d. 211), and the Kitab al-amwal of Ibn Zanjawayh (d. 251). The second consists of literary sources of adab and tarikh, such as the Maghazi of al-Waqidi (d. 207), the Futuh of al-Baladhuri (d. 279), and Al-Kamil fi 'l-adab by Ibn al-Mubarrad (d. 286). By using these sources to chart the conceptual history of the kharaj, I pay attention to three particular issues. First, how was the kharaj theoretically defined and deployed, and with which terms and concepts (for example, the jizya, fay’, or ghanima) was it associated? Second, how did the kharaj as a theoretical institution change over time, and to what can these changes be said to correspond? Finally, how did the genre in which the kharaj was discussed affect its meaning? For example, what was the difference between discussions of the kharaj in adab, fiqh, or futuh and maghazi literature? Ultimately, I argue that the development of the fiqh and the evolution of the madhhab structure restricted the kharaj to a particular juridical definition, while at the same time expanding its valences to include novel concepts and practices.