Context: The poet recalls an experience from the time of the captivity of the Israelites in Babylon. The prisoners, who sit weeping on the river banks of Babylon, and remember Jerusalem, hang their harps on trees beside the river because their captors have demanded that they amuse them with Jewish songs. The Israelites, however, cannot sing their songs in a foreign, or unclean, land. Declaring his devotion to Jerusalem, the psalmist utters a vehement curse against the Edomites, the descendants of Esau who abetted the Babylonians in their destruction of Jerusalem and the temple. Describing the plight of the captured Israelites, the poet says: