7 For if that first covenant had been faultless, then should no place have been sought for the second.
This is not a testament. You can't replace a testament with a second one, because once the person dies the testament is sealed in that blood.
8 For finding fault with them, he saith, Behold, the days come, saith the Lord, when I will make a new covenant with the house of Israel and with the house of Judah: 9 Not according to the covenant that I made with their fathers in the day when I took them by the hand to lead them out of the land of Egypt; because they continued not in my covenant, and I regarded them not, saith the Lord. 10 For this is the covenant that I will make with the house of Israel after those days, saith the Lord; I will put my laws into their mind, and write them in their hearts: and I will be to them a God, and they shall be to me a people: 11 And they shall not teach every man his neighbour, and every man his brother, saying, Know the Lord: for all shall know me, from the least to the greatest.
This is the new covenant. Paul talks of how our heart is circumcised with the true circumcision when we are crucified with Christ. Paul tells us that Christ lives in us, those laws are an expression of Jesus Christ in us.