When Moses received all of the laws that would define the Jewish tradition, he also received the explanation of these laws. The laws were contained in the Pentateuch, or Torah. These were written down on scrolls. The explanation however, was not allowed to be written down. Jews were obligated to speak the explanation and pass it on orally to students, children, and fellow adults. When Israel was eventually destroyed by Rome in 70 CE, Jews who memorized the explanation were being killed. In order that the explanation would not die as well, a Chief Rabbi, 200 years later had it written down. The Oral Law became the Talmud.
