Just moments before Moses delivers his major address outlining the commandments, a clear historical and geographical marker is established. The nation is transitioning from a period of constant war and wandering into a new era of settlement and stability, providing essential background for everything that follows.
Earlier events note that Moses began explaining the Torah after defeating the kings Sihon and Og. However, there is a deeper layer to this timeline. The teaching did not begin immediately following the military victories. Instead, Moses waited until the Israelites actually took possession of the land and actively divided it into permanent territories for the two and a half tribes [רמב״ן והטור הארוך].
This specific timing carries profound practical significance. The people needed to conquer a settled land and achieve a state of true stability first. Only when they could observe the commandments in a state of calm, free from the fear of terrifying enemies, was the moment finally right for Moses to begin explaining the Torah and guiding the Israelites on how to fulfill the commandments [ספורנו].
To ground these events geographically, the location across the Jordan River is defined precisely by the direction of the sunrise. This makes it clear that the events took place on the eastern side of the Jordan River, intentionally distinguishing it from the western side [רש״י].