The psalm, in its whole of nine verses, expresses longing for Jerusalem as well as wrath for the Holy City's foes, often with violent imagery. The hymn was assigned to the prophet Jeremiah by rabbinical sources, and the Septuagint version of the psalm carries the superscription "For David." Psalm 137 is one of the so-called "penal psalms," which describe the punishment that sin deserves. These poems usually begin with a statement of innocence (or ignorance) followed by a confession of guilt. They often include a call for justice, along with prayers for mercy. The poet of Psalm 137 fits this pattern: He begins by admitting his guilt (verse 1), asks for forgiveness (v. 4), and then pleads for justice to be done (vv. 5-9). This psalm has been interpreted as referring to many different situations or events in history. It has been suggested that it describes the exile of Judah from Israel, the destruction of both cities, or even the invasion of Egypt by the Assyrians. However, the language of verse 1 seems to rule out any such recent event as the exile, since the holy city was still inhabited at that time. Further, although Jerusalem did suffer destruction during the Babylonian captivity, there is no evidence that this fact formed the basis for the psalmist's complaint.