What does Psalm 137:7 mean?
Jacob was the patriarch of the nation of Israel (Genesis 32:28; 35:23–26). His twin brother was Esau (Genesis 25:24–26), patriarch of the nation of Edom (Genesis 25:30; 36:1, 8). When Babylon attacked Jerusalem (2 Chronicles 36:17–21), Edom did not merely stand by (Obadiah 1:10–11). They apparently helped the Babylonians capture Jews fleeing the carnage (Obadiah 1:13–14) and participated in sacking Jerusalem. Catastrophes are often referred to as "the day" in Scripture (Isaiah 9:4; Ezekiel 13:5; Joel 2:1; 2 Thessalonians 2:2; 2 Peter 3:12).Other Old Testament passages predict the Lord's judgment on Edom (Obadiah 1:1–4, 18; Ezekiel 25:12–14). Because of what the Edomites did during Jerusalem's destruction, the psalmist prays for divine vengeance (Obadiah 1:15). This idea of an enemy receiving the very evils they have done continues in the next verses (Psalm 137:8–9).