In Numbers 20, which nation refused to let Israel pass through its land on the King's Highway?

Answer: Edom

Moses promised to stay on the King's Highway and pay for any water, but Edom came out with a large army, so Israel turned away.

“But Edom answered, “You may not travel through our land, or we will come out and confront you with the sword.””— Numbers 20:18 (BSB)