This thesis examines the early Jewish reception of the love command (Lev 19:18) during the Second Temple period. Although the ascendancy of this command as the “greatest” command in later Jewish and Christian writings is well-known, the historical interpretative process through which this levitical love command came to be viewed as such is not widely known. The thesis begins by examining the meaning of Lev 19:18 in its original context and then systematically traces its interpretation in Second Temple, Jewish literature by carefully examining its citations in context. The study examines the Greek translation of Lev 19:18 in the Septuagint, followed by a series of sustained exegetical analyses of interpretations of Lev 19:18 in the Book of Jubilees, the Damascus Document, the Community Rule, Galatians, Romans, James, and the Synoptic Gospels. Although the citations of Lev 19:18 are infrequent in the Second Temple period, a careful consideration of each occurrence demonstrates diverse, if complex, developments vis-à-vis Lev 19:18. It is argued that no mainstream Jewish interpretation of Lev 19:18 existed during the Second Temple period, and the analysis repudiates a simplistic, evolutionary trajectory (e.g., from restricted, intra-communal obligation to universal altruism) regarding its interpretative development. The study concludes by identifying important areas of development that paved the way for Lev 19:18 to become the indispensable, hermeneutical key and summary command in Jewish and Christian thought.