In the fifth Aliyah of Ki Tavo, the Torah tells us of the Berachot and Klallot that were to be pronounced to all the people of Israel at Har Grizim and at Har Eval. The Torah then describes how the tribes of Israel were divided between the two mountains while the Leviim stood in the middle to pronounce the blessings and the curses. This event greatly parallels Matan Torah at Har Sinai. It seems that Hashem wanted to recreate the acceptance of the Torah for this new generation that would conquer Israel. Having this younger generation accept for itself the Mitzvot in Israel would be an important way of teaching them that the ultimate goal of living in Israel was the fulfillment of the Torah. Harav Eli Munk points out a difference between the two events. Here, the people were to stand ON the mountains-not at the foot of them. This shows that rather than simply accepting the laws passively, as they had at Har Sinai, the people could now express with confidence their commitment to uphold the Mitzvot. As opposed to those who stood at Sinai, these people had previously lived with and performed the Torah's laws all their lives and were now prepared to pass them on to the next generation.
Like the Jews at Sinai, we all begin our training in Torah rather passively. When we are young, we receive from others and work on making it part of our very being. But once we have reached the age of Mitzvot, we must begin reaching out to others, eventually teaching, guiding, inspiring and enriching the lives of the next generation. This is the process of Mesorah, transmitting the tradition from generation to generation. We must all recognize this responsibility we have as a part of Klal Yisrael.