This chapter examines the rhetorical strategies of the author(s) of one early Irish legal tract in order to explore what this can tell about religious discourse and theological concerns in early Irish law, particularly in relation to intersecting ideas of eschatology and reform. It focuses on apocalyptic and reforming discourse in one particular piece of legislation, that is, Cain Domnaig, the ‘Law of Sunday’, and deals with some wider considerations that take account of the jurisprudential writings of early medieval Ireland as well as promulgated law. There have been some tentative steps towards explicating the theological principles which underlie the morality codified in early Irish law, particularly in the major seventh-century collection known as the Senchas Mar. Eschatological rhetoric seems to have been an established feature of other promulgated law texts in early medieval Ireland. The prosimetric nature of the narratives is a common feature of early Irish literature of every genre, including legal texts.