The ancient patriarchs of Judaism are identified as Abraham, Isaac, and Jacob. According to Jewish tradition, God enters into a covenant, an event that helps to define the nature of Judaism, with Abraham by offering protection in exchange for the obligatory circumcision of all males as a sign of entering into the covenant. God's narrative gift to his chosen people was given to them in Hebrew, a divine language. By the post-Exilic period of Jewish history, Aramaic became the preferred language used to translate the Jewish Scriptures, and second century BCE marked a time when many Jews read a Greek Septuagint or an Aramaic version. Judaism considers sin to be impure because it stains the individual, similar to getting dirty, rendering one unable to uphold the covenant. In contrast to the earlier sectarian battles and their dogmatism, rabbinic Judaism defined itself in opposition to the former sectarian groups, reinvigorated Judaism, and preserved its identity.