PEIKEI AVOT 1:1 ‘MAKE A FENCE AROUND THE TORAH’

"Moses received the Torah from Sinai and transmitted it Joshua. Joshua transmitted it to the Elders, the Elders to the Prophets, and the Prophets transmitted it to the Men of the Great Assembly. They [the Men of the Great Assembly] said three things: Be deliberate in judgment, raise many students, and make a protective fence for the Torah."