“By the river of Babylon, there we sat down.” This psalm, 137, is important liturgically: some say it before bensching – saying grace after meals – during the week and part of it is sung at a wedding before smashing the glass.

Yet amid its plaintive poetry we ignore its angry, violent end: “Daughter of Babylon, doomed to destruction, happy is the one who repays you what you did to us, happy is the one that grabs and smashes your children on a rock.”

What do we do with this? We might hear the anger, but reject its violence. This final line expresses the fury of the vulnerable and dispossessed, of those who have almost lost everything.

The psalm can make us more sensitive to anger, both of others and our own. After all, anger can be the engine of determined social change; it teaches us that a better world is necessary.

Yet violence, as we see all too often, can destroy worlds.  The violent language that can accompany hot anger, in its rawness, must be transformed into the cool resolve to work towards a better future.

The symbolic image of infanticide makes us profoundly uncomfortable, but the psalm itself hits us with violence while pointing towards a discomfort with violent feeling.

‘Happy is the one who smashes your children on a rock’. No one can be happy to feel or say such a thing. The language used echoes other psalms and emotional states of true happiness.

The psalm expresses violence and gestures towards a broader perspective when such feelings will pass. It makes us aware of a time when people will live with dignity in peace.

We can work to make things better and cultivate a future when we will truly be able to sing a song of the merciful.

υ Benji Stanley is Reform Judaism’s young adult development rabbi