Early on in Parshas Nitzavim we get directions about atzvah that we are assured is not far from us (30:11),:
כִּי הַמִּצְוָה הַזֹּאת אֲשֶׁר אָנֹכִי מְצַוְּךָ הַיּוֹם לֹא נִפְלֵאת הִוא מִמְּךָ וְלֹא רְחֹקָה הִוא
A few verses later (14), it is said to even be very כִּי קָרוֹב אֵלֶיךָ הַדָּבָר מְאֹד בְּפִיךָ וּבִלְבָבְךָ לַעֲשׂתוֹ: us, in our mouths and hearts.
כִּי קָרוֹב אֵלֶיךָ הַדָּבָר מְאֹד בְּפִיךָ וּבִלְבָבְךָ לַעֲשׂתוֹ
My grandfather cites the Ramban's explanation of the mitzvah in question and offers some of his own insight. I won't cover the entire piece but focus on the part in which he addresses the Ramban's take on this as referrring to kol haTorah kula. (The other view is that it refers to the mitzvah of tshuva).
My grandfather ask, according to the Ramban's take, why refer to what is in your mouth בְּפ…