Albert Barnes Commentary Ezekiel 4:12

"And thou shalt eat it as barley cakes, and thou shalt bake it in their sight with dung that cometh out of man." — Ezekiel 4:12 (ASV)

In eastern countries where fuel is scarce the lack is supplied by dried cow-dung stored for the winter. Barley cakes were (and are) baked under hot ashes without an oven. The dung here is to be burned to ashes, and the ashes used in this way.