John Calvin Commentary Psalms 137:7

"Remember, O Jehovah, against the children of Edom The day of Jerusalem; Who said, Rase it, rase it, Even to the foundation thereof." — Psalms 137:7 (ASV)

Remember, O Jehovah! the children of Edom. Vengeance was to be executed upon the other neighboring nations that had conspired to destroy Jerusalem, so that they are all undoubtedly included here under the children of Edom, who are specified, a part, for the whole. This was either because they showed more hatred and cruelty than the rest, or because their cruelty was not so easily borne, considering that they were brothers and of the same blood, being the descendants of Esau, and that the Israelites had, by God’s commandment, spared the Edomites when they devoted all others besides them to destruction (Deuteronomy 2:4).

It was, therefore, the height of cruelty for them to invite the Babylonians to destroy their own brothers, or to fan the flames of their hostility. We are to notice, however, that the Psalmist does not break forth into these awful denunciations rashly, but as God’s herald, to confirm former prophecies.

God had predicted through both Ezekiel and Jeremiah that he would punish the Edomites (Ezekiel 25:13; Jeremiah 49:7; Lamentations 4:21–22), and Obadiah distinctly gives the reason, consistent with what is stated here—that they had conspired with the Babylonians (Obadiah 1:11). We know that God intended in this way to comfort and support the minds of the people under a calamity so distressing that Jacob’s election might have seemed frustrated if his descendants were treated with impunity in such a barbarous manner by the descendants of Esau.

The Psalmist prays, under the inspiration of the Spirit, that God would practically demonstrate the truth of this prediction. And when he says, Remember, O Jehovah! he thereby reminds God’s people of the promise, to strengthen their belief in God's avenging justice, and to make them wait for the event with patience and submission.

To pray for vengeance would have been unjustifiable if God had not promised it, and if the party against whom it was sought had not been reprobate and incurable; for concerning others, even our greatest enemies, we should wish for their amendment and reformation. The term day of Jerusalem, is a title he uses, and one of frequent occurrence in Scripture, for the time of visitation, which had a divinely appointed and definite duration.