Commentators explain that the "uncircumcised ear" is a powerful metaphor for a heart that is spiritually deaf and resistant to God's word. Just as physical circumcision was a sign of covenant, a "circumcised ear" is one consecrated to hearing and obeying God. The prophets warned that an external religious sign, like circumcision (or baptism for Christians), is meaningless if the heart remains rebellious and closed off to God's truth.