Mount Seir was in the most prominent mountain range of the country of Edom, and used as a synonym for the whole nation. It was situated southeast of the Dead Sea and contained generally poorer land than the areas the Caananites and then the Israelites occupied. History between Edom and Israel had generally not been pleasant, going all the way back to their founding fathers, Esau and Jacob.
This prophecy comes against Edom because of the enmity they maintained against Israel. The Lord mentions the time of Israel’s calamity and final punishment, and I can’t tell if that’s relative to Ezekiel’s time period or to the end of days like the last chapter, referring to the Tribulation or Daniel’s Seventieth Week. In either case, Israel is made desolate, and Edom rejoiced over this, therefore the Lord will bring a sword against Edom and make it desolate in return.
Beyond just gloating over Israel’s downfall, Edom desired to take possession of the land that was not promised to them. The Lord’s promises remained in effect even while He was chastising His people for the sins they had been committing. As we have seen, He always planned to restore the righteous remnant to the land He gave their fathers after purifying them through the trials they faced. In contrast to Edom’s envy, the Lord protected Edom from Israel when they marched to conquer Canaan. The most direct route was through Edom’s territory, and Israel asked Edom to be granted safe passage through, purchasing food and provisions along the way instead of just raiding for them. Edom refused, so the Lord led Israel the long way around instead of sending retribution against Edom.
You are patient, but Your mercy is not extended forever. Just because things have gone on for a long time doesn’t mean they last forever.