bringing and keeping faith

John Piper:

To guarantee that this covenant [re: Jer 31.31-34] will not fail, Christ takes the initiative to create the faith and secure the faithfulness of his people. He brings a new-covenant people into being by writing the law not just in stone, bot on the heart. In contrast with the :letter" on stone, he says "the Spirit gives life" (2 Cor 3.6). "When we were dead in our trespasses, [God] made us alive together with Christ" (Eph 2.5). This is the spiritual life that enables us to see and believe in the glory of Christ. This miracle creates the new-covenant people. It is sure and certain because Christ bought it with his own blood.

And the miracle is not only the creation of our faith, but the securing of our faithfulness. "I will make with them an everlasting covenant ... I will put the fear of me in hearts, that they may not turn from me" (Jer 32.40). When Christ died, he secured for his people not only new hearts but new security. He will not let them turn from him. He will keep them. They will persevere. The blood of the covenant guarantees it.