Can someone help me with this CS Lewis reference?

Years ago, I read an essay by CS Lewis in which he commented about those Psalms written in a despairing tone, in which the Psalmist complains about his or Israel's suffering. Lewis observed that a Greek poet of the same time period would never have written such a poem, since (according to Lewis) the Greeks did not even expect justice from their gods.

I thought this was so interesting that I soon read Lewis's "Reflections on the Psalms."

But I cannot remember where I read that original passage. (It was NOT in "Reflections on the Psalms.") Does anyone know the essay in which it appears? I know I read it in one of the anthologies of Lewis's writings.

Thanks