The book of Deuteronomy has as its main theme the covenant and its renewal. The unity of Israel is integral to the covenant relationship with God, and so the words of Moses are for all Israel.
The people hear these words beyond the region of the Jordan, in the land of Moab, though the specific location is uncertain.
1 These are the words that Moses spoke to all Israel beyond the Jordan in the wilderness, in the Arabah opposite Suph, between Paran and Tophel, Laban, Hazeroth, and Dizahab.