The foxes walk upon it - Foxes are very numerous in Palestine, see on Judges 15:4; (note). It was usual among the Hebrews to consider all desolated land to be the resort of wild beasts; which is, in fact, the case every where when the inhabitants are removed from a country.
The foxes - Or, jackals. As these animals live among ruins, and shun the presence of man, it shows that Zion is laid waste and deserted.