Albert Barnes Commentary Obadiah 1:11

"In the day that thou stoodest on the other side, in the day that strangers carried away his substance, and foreigners entered into his gates, and cast lots upon Jerusalem, even thou wast as one of them." — Obadiah 1:11 (ASV)

In the day that you stood on the other side – The time when they so stood is not defined in itself as past or future. It is literally, “In the day of your standing over against,” that is, to gaze on the calamities of God’s people; “in the day of strangers carrying away his strength,” that is, “the strength of your brother Jacob,” of whom he had just spoken, “and foreigners entered into his gates, and cast lots on Jerusalem, you too as one of them.” “One of them” they were not.

Edom was no stranger, no alien, no part of the invading army; he whose strength they carried away was, he had just said, his “brother Jacob.” Edom burst the bonds of nature to become what he was not, “as one of them.” He purposely does not say, “you too were (הית hayı̂tha) as of them,” as he would have said, had he wished to express what was past. Obadiah, seeing in prophetic vision the destruction of Jerusalem and the share which the Edomites took in it, describes it as it is before his eyes, as past.

We see before us, the enemy carrying off all in which the human strength of Judah lay—his forces and his substance—and casting lots on Jerusalem, its people and its possessions. He describes it as past, yet not more so than the visitation itself which was to follow some centuries afterward. Of both, he speaks alike as past; of both, as future. He speaks of them as past, as being so beheld in “His” mind in whose name he speaks.

God’s certain knowledge does not interfere with our free agency. “God compels no one to sin; yet, foresees all who shall sin of their own will.”

How then should He not justly avenge what, foreknowing, He does not compel them to do? For as no one, by his memory, compels to be done things which pass, so God, by His foreknowledge, does not compel to be done things which will be. And as man remembers some things which he has done, and yet, has not done all which he remembers, so God foreknows all things of which He is Himself the Author, and yet is not Himself the Author of all which He foreknows. Of those things then, of which He is no evil Author, He is the just Avenger.