Jacob echoes a sentiment for the brass plates here:
Deut. 30:6 And the LORD thy God will circumcise thine heart, and the heart of thy seed, to love the LORD thy God with all thine heart, and with all thy soul, that thou mayest live.
Jer. 4:4 Circumcise yourselves to the LORD, and take away the foreskins of your heart, ye men of Judah and inhabitants of Jerusalem: lest my fury come forth like fire, and burn that none can quench it, because of the evil of your doings.
The image of circumcising the heart was long with Israel, even if became one of the major tasks of Jesus to remind them of the need to internalize the teachings of God (the text of the Sermon on the Mount is the best example of this).