Jeremiah 31
33 But this shall be the covenant that I will make with the house of Israel; After those days, saith the Lord, I will put my law in their inward parts, and write it in their hearts; and will be their God, and they shall be my people.
34 And they shall teach no more every man his neighbour, and every man his brother, saying, Know the Lord: for they shall all know me, from the least of them unto the greatest of them, saith the Lord: for I will forgive their iniquity, and I will remember their sin no more.
35 Thus saith the Lord, which giveth the sun for a light by day, and the ordinances of the moon and of the stars for a light by night, which divideth the sea when the waves thereof roar; The Lord of hosts is his name:
36 If those ordinances depart from before me, saith the Lord, then the seed of Israel also shall cease from being a nation before me for ever.
37 Thus saith the Lord; If heaven above can be measured, and the foundations of the earth searched out beneath, I will also cast off all the seed of Israel for all that they have done, saith the Lord.
The new covenant is promised to Israel and it`s a contract that will be executed by Jesus Christ when He returns to rule. The church is part of covenant Israel, Gentiles grafted in, 1st resurrection already taken place.
Believers are ministers of the New Testament which is the gospel, we execute his will/testament and represent as His Spirit gathers what is His. Jesus gets his inheritence before the contract is implemented.