Morton Smith has pointed out that in the period of the Second Temple ‘Differences as to the interpretation of the purity laws and especially as to the consequent question of table fellowship were among the principal causes of the separation of Christianity from the rest of Judaism and the early fragmentation of Christianity itself.’ In his introductory study of purity in Judaism Jacob Neusner adds, ‘purity is an essential element in the interpretation of Israel's total religious system’. The idea of purity itself has long been of interest to anthropologists, for a concern with the clean and unclean stretches far beyond the confines of the religion of Judaism. It is, however, the rabbinic literature that attests to its special importance in the Jewish tradition. It is only recently, though, that the role of purity within Judaism has been made the subject of specific critical studies. Jacob Neusner has surveyed the topic and has since embarked on a detailed study of the legal traditions concerning purity.

Neusner, however, is primarily concerned with the way in which the purity idea was employed after the destruction of the Temple while we, in this study, shall examine the concept of purity as it appears in two sources, the Dead Sea Scrolls and the letters of Paul, which have their origin before AD 70.