Kosher dietary laws come from two sources in Judaism. The first source is the Scriptural source: the set of laws, rules, and protocol found in the Torah. These scriptures outline specific rules concerning forbidden and permitted animals, lawful slaughter, the correct use of utensils, laws for passover and fasting, and lawful sacrifice.
Kosher law is further developed in the second source, the talmudic tradition. The Talmudic tradition is the oral tradition of the rabbis passed down from geneartion to generation. Within the Talmudic tradition, kosher law has changed and evolved to address the concerns of modern living. For example, most foods have artificial preservatives and other lab-produced ingredients. These ingredients present special problems when considering Kosher dietary restrictions. Rabbis continue to expand, refine, and clarify the original dietary laws in order to address these problems.
Furthermore, a number of dietary laws related to sacrifice are only relevant for those living in Jerusalem, as they can only be enacted at the Second Temple. Thus, the rabbinical tradition also provides clarification concerning the way in which devout followers can maintain Kosher diets and traditions outside of the city of Jerusalem.