Hakdama of Rambam to Mishna 1

Know that each commandment that the Holy One, blessed be He, gave to Moshe, our teacher – peace be upon him – was given to him with its explanation. He would say to him the commandment and afterward tell him its explanation and content; and [so too with] everything that is included in the Book of the Torah. And the manner of its teaching to Israel is as it is said (Eruvin 54b – in Chapter 5), Moshe would enter his tent, and Aharon would enter it first, and Moshe would tell him the commandment that was given to him, and teach him its explanation one time. And [then] Aharon withdrew and retreated to our teacher, Moshe's, right, and Elazar and Itamar, his sons, entered after him. And Moshe would tell them what he told Aharon. And they withdrew, and one sat to our teacher, Moshe's left and the second to the right of Aharon. 

And afterward, the seventy elders came, and Moshe taught them as he taught Aharon and his sons. And afterward, the masses and 'all who sought the Lord' came and He placed that commandment in front of them, [and so forth] until they heard everything from his mouth.
It came out that Aharon heard that commandment from the mouth of Moshe four times, his sons three times, the elders twice and the rest of the people once. And Moshe withdrew, and Aharon reviewed the explanation of that commandment which he learned – that he heard from the mouth of Moshe four times, as we said – to all those present. 

And Aharon retreated from them, after his sons had heard the commandment four times – three times from the mouth of Moshe, and once from the mouth of Aharon. And Elazar and Itamar reviewed [it,] to teach that commandment to all the people that were present, after Aharon withdrew. And they withdrew from teaching. And it came out that the seventy elders heard the commandment four times – two from the mouth of Moshe, one from the mouth of Aharon and one from the mouth of Elazar and Itamar. And afterward, the elders also reviewed [it,] to teach the commandment to the masses one time. 

It came out that the entire congregation hears that commandment four times – once from the mouth of Moshe, once from the mouth of Aharon, a third [time] from the mouth of his sons and a fourth [time] from the mouth of the elders.
And afterward all the people went to teach – each person his neighbor – all that they heard from the mouth of Moshe – and write that commandment in scrolls. And the officers would circulate to all of Israel to teach and correct, until [the people] knew the commandment by heart and became accustomed to reading it. And afterward, they taught them the explanations of that commandment that was given from God – and that explanation would include [many] matters. And they would write the commandment and study [it] according to the received tradition.