The third aliyah of Parashat Ki Tavo contains a reference to the Torah being commanded "today." Rashi says that this means we should treat the Torah as though it were fresh and new every single day of our lives. Ibn Ezra demurs and says that the word "today" was a reference to the day in Moshe's life when these words were first said. Netziv says something more subtle: "Today" refers to the moment when Moshe said those words, which were prior to the forging of a covenant in Moav (just prior to Moshe's death). With the forging of this covenant, there would be no additional mitzvot from God. However, the job of interpreting and explaining the Torah and deriving new understandings continues into future generations and in this way the Torah remains fresh and relevant.
היום הזה. ידוע הדרש שהביא רש״י בכל יום יהיו בעיניך כחדשים. אבל אין מקרא יוצא מדי פשוטו. שמדבר ביחוד באותו יום שעומד בו. ובא לאפוקי מאז שעמדו על הר סיני עד היום הזה. וענין פרשה זו. הוא הקדמה וביאור לכריתת ברית שבא אחריו הברכות והקללות שנקרא ברית שבערבות מואב. ונתוסף בו ענין א׳ מאד נעלה על ברית שבהר סיני. היינו מה שנזהרו עתה על שקידת התורה לחדש בה דינים עפ״י כללי התורה ודקדוקיה. וע״י משפטי התלמוד שלימד משה. והיינו דאי׳ בסוטה דל״ז א׳ גבי בו״ק ללמוד וללמד לשמור ולעשות. וכבר ביארנו בפ׳ אחרי הביאור ע״ז הלשון לשמור הוא לזכור מה שכבר למד. ולעשות הוא לחדש עוד...
The midrash that Rashi brings is known; we should view the Torah as being fresh each day. But Scripture does not fully depart from its plain sense meaning. This verse was said about a specific day on which it was said. And it comes to exclude everything other than during the duration of standing at Sinai to this day.
The point of this section, which is an introduction to the forging of the covenant which follows with the blessings and curses which are called "the covenant of Arvot Moav." And there is something special about this covenant which was not true about the covenant of Sinai and that is that we were commanded at this later time to study the Torah with diligence and to discover new rules by means of the principles of interpretation and careful reading, and through the laws of the Talmud which Moshe taught.
And this is what is found in Tractate Sotah 37a regarding the phrase "to learn and to teach to protect and to do." And I've already explained that the language of "protecting" is to remember what was already learned. And "to do" is to innovate something new.
"And you shall keep" this is the mishnah...and this means that anything which is investigated by one generation becomes "mishnah" tot he next generation...and when a new idea or instruction emerges through investigation and deep thought, that learning becomes mishnah afterwards. "And you shall do them" means to continue to investigate additional instructions and guidance and this is the learning of every generation.