It is the power of God to save people from their sins, for everyone who has faith, to the Jew first, and also to the Gentile. He would change the covenant. The externals change. There is no longer a need for the Temple sacrifices or the outward laws of impurity, such as the kosher laws. Messiah came as the final and ultimate sacrifice for all time.
True purity is a matter of the heart.
We are still to keep the moral commandments of the Torah, but the New Covenant, Jeremiah said, would be a matter of the heart. God would put the essence of the Torah in the hearts of his people. Fourth, God promised forgiveness of sin. Finally, God promised that through this New Covenant the whole world would come to know Him. God created us in his image to be holy and perfect.