It Deuteronomy 10:12-16, it instructs to circumcise our hearts and obey the Mosaic Law. In Deuteronomy 30:1-10, it prophesies about a time when the Israelites would return from exile, God would circumcise their hearts, and they would return to obedience to the Mosaic Law. In Ezekiel 36:26-27 and Jeremiah 31:33, they are speaking in regard to the New Covenant, the Israelites returning from exile, God circumcising their hears by means of the Spirit, and retuning to obedience to the Mosaic Law, where God will take away our hearts of stone, give us hearts of flesh, and send His Spirit to lead us in obedience to the Mosaic Law, and where He will put the Mosaic Law in our minds and write it on our hearts. In Romans 2:25-29, the way to recognize that a Gentile has a circumcised heart is by observing their obedience to the Mosaic Law, which is the same way to tell for a Jew, and circumcision of the heart is a matter of the Spirit, which is in contrast with Acts 7:51-53, where those who have uncircumcised hearts resist the Spirit and do not obey the Mosaic Law. So the New Covenant is all about the Israelites returning to obedience to the Mosaic Law and having a circumcise heart does not refer to anything other than them living in obedience to it.