Even though Israel and Edom were kinfolk, that didn’t mean they were immune to a little old-fashioned animosity. Ever since the two brothers, Jacob and Esau, departed from each other in Genesis 33-35, their descendants remained at war.
That continued on into the Exodus. Moses records that most of the nations in the wilderness saw the prospect of a two-million-member-former-slave-nation as a huge threat, especially after hearing of what their God had done to deliver them from Egypt.
Exodus 15:14-16 says that the Philistines were “anguished,” the Moabites “trembled,” and the inhabitants of Canaan simply “melted away.” As for the Edomites? They were simply “dismayed.”
It was a long time before Israel and Edom caught up for their long-waited reunion though, and Moses wanted to make sure Edom knew they weren’t coming for their land.
According to Moses’ own words in Deuteronomy 2:4-6, before Israel tried to pass through Edomite territory (in Numbers 20-21), they knew that not a single footstep’s worth of land would be given to them. They couldn’t provoke them even an inch; God gave Esau’s descendants Mount Seir just like He gave Canaan to Israel.
Furthermore, Israel offered to buy food and water from the Edomites rather than receive it directly—a standard part of Near Eastern hospitality, albeit not one usually given to enemy nations on the warpath.
The command from God was clear: Don’t provoke them, don’t try to take their land, and make every effort to ensure Edom knows Israel is not a threat.
It didn’t matter. As we know from Numbers 20-21, Esau refused entry to Israel, despite numerous pleas from Moses to allow Israel to simply pass through the land. The Edomites even threatened to send their army out to block them by force, if necessary (Numbers 20:18-21).
Moses repeats all this in Deuteronomy 2 to send a simple message, and it’s not just to remind them of their angry cousins to the south. It’s to tell them that despite Esau’s lack of hospitality, God still took care of them. They had enough resources to buy food and water for all those people, but even if the Edomite store was closed, they survived anyway. They “didn’t lack a thing.”
It’s unfortunate that Edom made enemies where they didn’t have to; indeed, this would be a major part of their condemnation later (Obadiah). But Israel did the right thing, and God made sure they were taken care of regardless of the actions of others.