Legs are not lips, and walking is not kneeling. And yet our legs uttered songs. Even without words, our march was worship. I felt my legs were praying. For Heschel, prayer wasn't only about words.
Prayer is, above all, communicating our ideals.
Marching for civil rights was a form of worship for Heschel because it was an expression of sacred ideals. Prayer from the siddur, within the walls of the synagogue, is not sufficient. To worship God most fully, we must be active in causes that stem from the values honored by the Jewish tradition. We must pray with our legs, not only our mouths.