From Sinai to the Present
After God gave the Torah to Moshe on Mt. Sinai, Moshe taught the Torah—that is, all of the understanding of the Oral Law—to others. First among these was his devoted student Yehoshuah (Joshua), who became leader of the Jewish People following the death of his teacher. Maimonides explains this in the introduction to his legal code:
All of the Torah, Moshe our Teacher wrote it in his own hand before his death. And he gave a Book to each and every tribe, and one Book he gave to be placed in the Ark of the Covenant for eternity … But the Commandment, which is the explanation of the Torah, he did not write down. Rather, he commanded it to the Elders and to Yehoshuah, and to all of the rest of Israel … Although the Oral Torah was not written down, Moshe our Teacher taught it in its entirety in his Legal Court to the Seventy Elders. And Elazar and Pinchas and Yehoshuah, these three received it from Moshe. And Yehoshuah, who was the student of Moshe our Teacher, to him he transmitted the Oral Torah, and commanded him concerning it.
This was the beginning of a long and unbroken chain of Mesorah, of transmission, as outlined by Maimonides in the same introduction. In each generation, there were many great scholars—but, nonetheless, each had one or more giants of Torah learning who were recognized as the leading authorities of the era. The transmission of the Oral Law continued without interruption until it was recorded in 3948 (188 C.E..), 1,500 years after it was given.