Rashi on TanakhPsalms 137

By the rivers of Babylon, there we sat when we went down into exile, and Nebuchadnezzar asked them to sing for him as they used to sing on the stage.

On willows Willows of the brook.

and our tormentors mirth Heb. ותוללינו, kinds of musical instruments that they hang up. This is how Menachem interpreted it (p. 184): וְתוֹלָלֵינוּ שמחה, and our musical instruments of joy. וְתוֹלָלֵינוּ can also be interpreted as: our enemies who would scorn and mock and joke with us, an expression of (102: 9): “those who scorn me (מהוללי) swear by me.”

If I forget you, O Jerusalem The congregation of Israel says this.

If I do not bring up Jerusalem The remembrance of the mourning of its destruction I shall bring up to mention at the head of every joyous occasion of mine.

Raze it Heb. עָרוּ is an expression of destruction, and so (Jer. 51:58): “The broad walls of Babylon shall be overthrown (תתערער),” and so (Hab. 3:13): “baring (ערות) the foundation.” It is used only for something whose roots are uprooted from the ground.