Psalm 137 is recited on the eve of Tisha B'Av, which commemorates the destruction of both Temples. It opens the liturgy, and sets the tone for the day. The liturgy of Tisha B'Av includes a wide array of kinot, poems of sorrow and mourning, giving voice to themes of exile and longing. But this ancient psalm, older than the kinot, captures the pain of exile from the Land of Israel perhaps most eloquently of all. The psalm is short -- only nine verses -- and can be divided into three parts, each with its own themes and challenges for today's spiritual yearners. The first four verses read as follows:

By the rivers of Babylon, there we sat, sat and wept, as we remembered Zion.

There on the poplars we hung up our lyres,

for our captors asked us there for songs, our tormentors, for amusement:

"Sing us one of the songs of Zion."

How can we sing a song of the LORD on alien soil?

In these opening lines, we can hear the sadism of the locals as they mock the newly-arrived Israelites: "Sing us one of those spirituals from the Old Country..." Some scholars remark that the Israelite response, "How can we sing... on alien soil?" reflects another aspect of loss: the poet, like many of the exiles, is wondering whether the God of Israel can hear or act when the people are no longer in their homeland. Perhaps prophecy and prayers only "work" when the People of Israel are located in the Land of Israel? This is more than a rhetorical question: the exile commemorated on Tisha B'Av is not only about distance from a physical place, but also from God. That distance is the cause of pain and loneliness that is reflected in the psalm.

If I forget you, O Jerusalem, let my right hand wither;

let my tongue stick to my palate if I cease to think of you,

if I do not keep Jerusalem in memory even at my happiest hour.

Here, the pain of loss melts into resolve. The poet doesn't know if God has forgotten, but the poet has not forgotten! The Temple in Jerusalem was the place where God and the people found great intimacy. The memory of this closeness is what Tisha B'Av is ultimately about: not a longing for sacrifices, but for the intimacy with God that worship evoked.

These lines are reflected in some well-known Jewish customs. In many times and places, Jews would leave a wall of their home unfinished or unpainted. This was a reminder that wherever the householder lived, it was still a place of exile until Jerusalem and its people would once again be whole. This practice is first described in the Talmud, Bava Batra 60b.

Another famous Jewish ritual reflects these verses: breaking a glass at a wedding. After all, surely the moment a couple is married must be their "happiest hour." Shattering a glass at this moment reminds onlookers of the work still to be done, although perhaps this couple's love is a step in bringing unity back to a fragmented world.