Moses preaches the teaching of Sinai. After all, the original covenant and law are still there. Life is still the motive and the goal. New occasions teach new duties. No canonical text is ever completed, fossilized, and absolutized.
Boundary situations require new words about old words.
So Deuteronomy takes the ancient traditions of the Mosaic age, itself on the boundary between wilderness and land, and restates, that is to say, reinterprets them in a vital way for later generations facing new occasions on new boundaries. This Bible of words shows us how to appropriate the faith of our ancestors. Yet in these interpretive moves Deuteronomy assures us paradoxically that not a jot, not a tittle will pass away. This wondrous blending of past, present, and future witnesses to both the stability and adaptability of sacred scripture. But we know, as does Deuteronomy, that the Bible offers us more and other than life.