The answer is: Moses

Deut 1:1

As the principal voice throughout Deuteronomy, Moses takes center stage as both the storyteller and the legislative authority of the Israelite community. Having led the Exodus and witnessed the struggles of his people in the wilderness, Moses stands poised to deliver a series of farewell speeches that encapsulate the lessons and commandments meant to guide the Israelites into their promised land.

What’s fascinating is how the very name “Deuteronomy” translates to “Second Law.” This isn’t merely a repetition; rather, it’s a chance for fresh understanding and renewed commitment to the covenant with God, specifically tailored for a new generation entering Canaan. By revisiting the laws, Moses ensures that they resonate with his audience, reinforcing the moral and ethical obligations required to maintain harmony in the new society.

Trivia alert! Did you know that the last chapter of Deuteronomy (Chapter 34) includes the account of Moses' death, which many scholars believe may have been written by a later author? This chapter also serves as a poignant conclusion to the Torah, underscoring Moses’ unique excellence as a prophet. It conveys divine approval of Moses by stating that "no prophet has arisen in Israel like Moses."

Understanding Deuteronomy is essential as it lays the groundwork for many core principles that will echo throughout later biblical texts, making it a cornerstone of history, ethics, and spirituality in the Judaic tradition.