John Gill Commentary Ezekiel 35:15

"As thou didst rejoice over the inheritance of the house of Israel, because it was desolate, so will I do unto thee: thou shalt be desolate, O mount Seir, and all Edom, even all of it; and they shall know that I am Jehovah." — Ezekiel 35:15 (ASV)

As you did rejoice at the inheritance of the house of Israel, because it was desolate

So Edom rejoiced at the destruction of Jerusalem, (Obadiah 1:12) , and so the followers of the man of sin will rejoice at the slaying of the witnesses, (Revelation 11:10) , which is resented by the Lord, and therefore adds, so will I do unto you ;

make you desolate, as is explained in the next clause: you shall be desolate, O Mount Seir, and all Idumea, even all of it ; not that mount only, but all the land of Edom, called Idumea; the destruction shall be general, as it was, and irretrievable; and so not Rome only, but all the antichristian states, will be destroyed, when God comes forth in his wrath against them:

and they shall know that I am the Lord ; the Lord God omniscient and omnipotent; who, having foretold all this, shall accomplish it.