Have you heard the Old Testament is the New Testament concealed and the New Testament is the Old Testament revealed? Besides this overarching thematic there are some very direct linkages from the OT to the NT that allow us to see the story of the gospel all through the ages.
Check out this powerful direct connection of an OT concept with a NT definition and application in the book of Jeremiah. This entire chapter is about truly knowing and following God and him being available to all people, not just the Jews.
In Jeremiah 9:25,26
“The days are coming,” declares the Lord, “when I will punish all who are circumcised only in the flesh— Egypt, Judah, Edom, Ammon, Moab and all who live in the wilderness in distant places. For all these nations are really uncircumcised, and even the whole house of Israel is uncircumcised in heart.” (my emphasis)
This is directly related to the NT concept of circumcision being “of the heart”. Here he was addressing Jews, showing them that it is not their ancestral inheritance, that make them true followers of God. Rather it is a spiritual reception God and truly living it out, not by religious outward rituals but by one’s changed and obedient life.
In Romans 2:29 Paul states: “A person is not a Jew who is one only outwardly, nor is circumcision merely outward and physical. No, a person is a Jew who is one inwardly; and circumcision is circumcision of the heart, by the Spirit, not by the written code. Such a person’s praise is not from other people, but from God. (my emphasis)
The thread of our Creator’s consistent love and character through his interaction with humanity over thousands of years of history documented in the bible is a wonderful guide. The encouraging and instructive stories of people interacting with him and direct commands from him pave our way to knowing and loving him and navigating our lives on this side of heaven. Thank you God.