God gave Abraham and his descendants the mark of circumcision as a physical reminder that they were cut out from the world, that is, set apart to serve the one, true Lord (Gen. 17:1–14). Every male that was circumcised under the administration of the covenant was, along with his family, “branded” by Yahweh. Even though God, as the universe’s Sovereign, owns everything He has made (Ps. 50:10), He revealed that He owns the covenant community in a unique way by His mark of circumcision. He has a special love for His people, and, consequently, if they break the terms of His covenant, they will endure a greater wrath than those whom He has not branded (Gen. 17:9–14; Jer. 4:3–4; Heb. 6:1–8).
Keeping the covenant has never been the means by which God’s people earn a righteous standing in His eyes. Instead, it demonstrates the delight they have in belonging to Him and their consent to His ownership of them by faith in His goodness and promises; faith is the only way those who have been marked can enjoy the full benefits that come with belonging to Him (Rom. 4). Circumcision, as the mark of the old covenant, never guaranteed that the Israelites would rejoice by faith in God’s special ownership of them, but the sign pointed to their need for their hearts to be set apart to love Him (Deut. 10:12–22).
The need for circumcision in the heart is the plain teaching of today’s passage. Jeremiah was sent to preach to the covenant community of Israel and call the people to repent and turn from their idolatry — refusal to recognize God’s rightful ownership of them. In Jeremiah 4:1–4, the prophet reminds the people that they cannot rightfully trust in the mark of circumcision for covenant blessings; rather, they have to experience the inner reality of a circumcised heart that the circumcision in their flesh is to signify. The Lord’s covenant of salvation has always been a covenant of the heart.
Verses 1–2 link circumcision of the heart with the salvation of Israel and the salvation of the Gentile nations. If the people would have turned from idolatry and honored their covenant with the Lord, Israel would have fulfilled its vocation to be a light to the world that illumined the path to the only redeemer God (Isa. 43:11; 60).