Ezekiel 4:15

‘Then he said, “I have given you cow's dung for man's excrement, and you shall prepare bread on it.”

God allowed him to use cow dung instead of man's excrement. Cow dung was a recognised fuel used by many for cooking. Why then should God have required something that he knew would appal Ezekiel, and then made such a concession? The answer must be that it was in order to draw attention to the point in question. The uncleanness in which His people were involved. Once that was done, and the horror of their position had got over to Ezekiel, the concession could be made. It was after all only a symbol. Nothing crucial depended on it. (This brings out that all these actions were seen as symbols and not sympathetic magic. In the latter case the rules could not have been broken or else the magic would not have worked).