In chapter 3, Yirmiyahu presents a prophecy that portrays the difficulty inherent in the repentance of the Jewish People through a parable. Israel is compared to a woman who has left her husband – God - for other men - idols. Such a woman is halakhically forbidden to return to her first husband and that sin pollutes and defiles the Land of Israel. Can Israel possibly return to God?
See Rabbi David Sabato's article on this topic here.