The term "uncircumcised in heart" is a metaphorical expression found in the Bible, used to describe a spiritual condition of insensitivity or rebellion against God. It signifies a lack of genuine faith, repentance, and obedience, contrasting with the physical act of circumcision, which was a sign of the covenant between God and His people, Israel.

Biblical References:

1. Leviticus 26:41 : "And I acted with hostility toward them and brought them into the land of their enemies. Then their uncircumcised hearts will be humbled, and they will pay for their iniquity." Here, God speaks of the Israelites' need for humility and repentance, indicating that their hearts were resistant to His commands.

2. Deuteronomy 10:16 : "Circumcise your hearts, therefore, and stiffen your necks no more." This command from Moses calls the Israelites to a deeper, internal transformation, urging them to remove the spiritual barriers that prevent them from fully following God.

3. Jeremiah 4:4 : "Circumcise yourselves to the LORD; remove the foreskin of your hearts, O men of Judah and people of Jerusalem, or My wrath will break out like fire and burn with no one to extinguish it, because of your evil deeds." The prophet Jeremiah warns the people of Judah and Jerusalem to repent and turn back to God, emphasizing the need for a heart change rather than mere outward compliance.

4. Jeremiah 9:26 : "Egypt, Judah, Edom, the Ammonites, Moab, and all who live in the desert in distant places. For all these nations are uncircumcised, and even the whole house of Israel is uncircumcised in heart." This passage highlights that both Gentiles and Israelites can be spiritually uncircumcised, indicating that true circumcision is a matter of the heart.

5. Ezekiel 44:7 : "In addition to all your other abominations, you brought foreigners uncircumcised in heart and flesh into My sanctuary to profane it—My house—and offered My food, the fat and the blood, and you broke My covenant." Ezekiel condemns the Israelites for allowing those who are spiritually and physically uncircumcised to defile the temple, underscoring the importance of spiritual purity.

6. Acts 7:51 : "You stiff-necked people with uncircumcised hearts and ears! You always resist the Holy Spirit, just as your fathers did." Stephen, the first Christian martyr, accuses the Jewish leaders of resisting God's Spirit, equating their stubbornness with being uncircumcised in heart.

Theological Significance:

The concept of being "uncircumcised in heart" serves as a powerful reminder of the necessity for inner transformation and genuine devotion to God. It underscores the biblical teaching that true faith is not merely about external rituals or heritage but involves a heartfelt commitment to God's will. This theme is consistent throughout both the Old and New Testaments, emphasizing that God desires a relationship with His people that is marked by sincerity, humility, and obedience.

In the New Testament, the Apostle Paul expands on this idea, teaching that true circumcision is a matter of the heart, accomplished by the Spirit (Romans 2:29). This spiritual circumcision is available to all believers, Jew and Gentile alike, through faith in Jesus Christ. It reflects the transformative work of the Holy Spirit in the believer's life, leading to a renewed heart and mind that align with God's purposes.