We read right at the beginning of Devarim that in that 40th year, the final year in the desert, “ho’il Moshe be’er es haTorah ha’zos,” Moshe began (Rashi: ho'il = started) to explain the Torah to Klal Yisrael.
He just began teaching Torah then? What had Moshe been doing for the past 40 years?
A few week's ago I contrasted the generation that heard Hashem’s words directly at Sinai with this new generation in year 40 who was expounding and explaining Torah through derashos and Torah she’ba’al peh, through their own initiative and process of discovery. There would be no Moshe to dictate answers to them in the future; answers would have to come through their own learning. Sefer Devarim is the boundary marker between the old and the new. Moshe is still there, but he is speaking with his own voice, not merely transmitting what G-d dictated. Moshe created a beginning – a starting point for the process of talmud Torah that we have been engaged in and continuing for over 3000 years since. He began teaching again in a different way, to a different people than the one's he took out of Egypt. (Sefas Emes)
The Midrash Tanchuma connects the אֵלֶּה הַדְּבָרִים of our parsha with a pasuk in Yeshayahu 43:16 אָשִׂים מַחְשָׁךְ לִפְנֵיהֶם לָאוֹר וּמַעֲקַשִּׁים לְמִישׁוֹר אֵלֶּה הַדְּבָרִים עֲשִׂיתִם וְלֹא עֲזַבְתִּים...: Just as G-d performed miracles for us in the desert, the "eileh ha'devarim" of our parsha, in the time of the future geulah G-d will do those same miracles, turning darkness to light and bending twisted paths straight, "eileh ha'devarim asisim v'lo azavtim."
What miracles is the Midrash speaking about that we see in the words "eileh hadevarim?"
It's the miracle of revealing Torah as it had never been revealed before.
The end of that pasuk in Yeshayahu is written in past tense, not the future tense (see Rashi). Shem m'Shmuel quotes the Midrash as explaining that the pasuk is referring to the miracle of Torah being revealed by Rabbi Akiva and his colleagues. The miracle Yeshayahu is talking about already happened! It's Torah which transforms darkness to light and guides us on the straight path. Even Moshe Rabeinu himself was in awe of the brilliance of R' Akiva's learning (Menachos 29) -- it was a miraculous phenomenon.
It's the same miracle which the "Eileh hadevarim" of our parsha is referring to -- our parsha is the beginning of that miracle unfolding, as Moshe began revealing Torah, giving us insight into how to expound and explain, of how to engage in learning Torah she'ba'al peh.
We are not Moshe Rabeinus, but we should learn from his life. The Torah he learned in year 40, the last year of his life, was not the same Torah he learned earlier. The generation he spoke to needed to hear a different message, be given different hadracha. The way he taught Torah in year 40 was different than the way he taught earlier. The world around us changes; the people around us change; we need to change as well. Why should we? Because that's the only way we can communicate with the next generation and make our message heard.