|SIDEBAR - "Unbroken Chain of Transmission"
The transmission from Moses until today is an unbroken chain of 120 generations. The following list of Rabbinic leaders from Moses until the completion of the Talmud in 500 CE appears in the introduction to Maimonides' "Mishneh Torah." Following this list is an explanation from Maimonides on the precise method of transmission, beginning with Moses.
Mount Sinai (1312 BCE)
The Elders (l260-860 BCE)
The Prophets (860-360 BCE)
The Great Assembly (360-260 BCE)
TANA'IM - Mishnaic Era (260 BCE - 200 CE)
AMORA'IM - Talmudic Era (200-500 CE)
MOSES' TEACHING PROCESS
Maimonides, citing sources from the Talmud and Midrash, recounts in graphic detail the transmission process from Moses to the people of Israel. Moses personally wrote 13 copies of the Torah and distributed them one to every tribe before his death.
Maimonides' "Introduction to the Mishnah"
Know that every mitzvah which G-d gave to Moses was given with its clarification. First He told him the mitzvah and then He expounded on its explanation and content, including all that which is included in the Torah.
The manner of transmittal to Israel occurred as stated in the Talmud (Eruvin 54b) [How was the system of teaching? Moses first learned the law from the mouth of the Almighty.]
Moses then went into the Tent, and Aaron went in with him. Moses then stated to him a single time the mitzvah he had received, and taught him its explanation, (following which) Aaron retreated to the right of Moses.
Then, Elazar and Itamar, Aaron's sons, entered and Moses told them what he had told Aaron, and then they stepped back. One sat to the left of Moses, and the other on the right of Aharon.
Then the seventy Elders arrived, and Moses taught Aaron and his sons. Following this came the masses of people and every one seeking God, and he (Moses) placed before them the mitzvah, until all had heard it from his mouth.
The result is that Aaron heard that precept from the mouth of Moses four times, his sons three times, the Elders twice, and the remainder of the people once.
Moses then left, and Aaron repeated the explanation of that mitzvah which he had learned, having heard it from the mouth of Moses four times (as we have mentioned), to all those present.
Aaron then left, after his sons had heard the precept four times (three times from Moses, and once from Aharon). After Aaron had departed, Elazar and Itamar repeated and taught that mitzvah to all the people present, and then ceased their teaching.
Thus we find that the seventy Elders heard the precept four times twice from Moses, once from Aharon, and once from Elazar and Itamar. The Elders themselves then repeated and expounded the mitzvah to the people one time. As a result, we find that the entire congregation heard the precept in question four times once from Moses, once from Aharon, a third time from his sons, and the fourth time from the Elders.
After this, all the people went to teach one another what they had heard from Moses and to write that mitzvah on scrolls. The leaders would roam through the Israelites to (insure that the people) learned and applied themselves until they would know the traditional version of that mitzvah and were fluent in reading it. They would then teach the explanations of that G-d-given precept. That explanation would include all aspects, and they would write the precept and learn by heart the Oral Tradition.
Thus, our Sages said in the Midrash "And G-d spoke to Moses at Mount Sinai" (Leviticus 25:1). Why does the Torah state specifically at Mount Sinai? Was not the entire Torah given at Sinai? This is to tell us that just as the law of the Sabbatical year was stated with its generalities, specifics and fine details at Sinai, so too all the mitzvahs were stated with their generalities, specifics and fine details at Sinai.
Maimonides - "Mishneh Torah," Laws of Sanhedrin 41-2
No one is qualified to act as judge in the Sanhedrin, or even in a court of three judges, unless he has been ordained by one who has himself been ordained. Moses ordained Joshua by laying his hands upon him, as it says (Numbers 27:23), "And he laid his hands upon him, and commissioned him."
Likewise, Moses ordained the seventy Elders, and the Divine Presence rested upon them. The Elders ordained others, who in turn ordained their successors. Hence there was an uninterrupted succession of ordained judges, reaching back to the tribunal of Joshua, indeed, to the tribunal of Moses...
What has been the procedure throughout recent generations with regard to ordination? It has been done not by the laying of hands upon the elder, but by designating him by the title "Rabbi," and saying to him "You are ordained and authorized to adjudicate (matters of Torah law)."