In describing how the entire nation became corrupt, Hashem declares “You are an uncleansed land.” This is reflective of the extreme spiritual sensitivity of Israel, a special characteristic of the land that appears throughout the Bible. Sinning inside the Holy Land affects not only the sinner, but the land itself becomes defiled as well (see Leviticus 18:24, Numbers 35:34). Thus, because of the sins of the nation, the land has become impure. Conversely, every act of goodness and kindness in Israel strengthens the land in addition to the people.
Source: Israel in the News