Luke 22:20, "And he did the same with the cup after supper, saying, “This cup that is poured out for you is the new covenant in my blood."
Christians don't agree on the meaning of this passage, some say it is a figure of speech others say that it is not. How do we settle the issue? The issue is settled by appealing to the final authority. The final authority is God, what does God say. So if all we have as to what God says is the written word of God then that is what we should appeal to.
What does scripture say is the blood of the new covenant?
It says the cup that is poured out for us is the new covenant in his blood.
There is nowhere else in scripture that explicitly states what the blood of the new covenant is. Hence the debate is over.