Now may the God of peace who brought again from the dead our Lord Jesus, the great shepherd of the sheep, by the blood of the eternal covenant, equip you with everything good that you may do his will, working in us that which is pleasing in his sight, through Jesus Christ, to whom be glory forever and ever. Amen. (Hebrews 13:20–21)
Christ shed the blood of the eternal covenant. By this successful redemption, he obtained the blessing of his own resurrection from the dead. That is even clearer in Greek than it is in English, and here it’s clear enough: “God . . . brought again from the dead our Lord Jesus . . . by the blood of the eternal covenant.” This Jesus — raised by the blood of the covenant — is now our living Lord and Shepherd.
And because of all that, God does two things:
he equips us with everything good that we may do his will, and
he works in us that which is pleasing in his sight.
The “eternal covenant,” secured by the blood of Christ, is the new covenant. And the new covenant promise is this: “I will put my law within them, and I will write it on their hearts” (Jeremiah 31:33). Therefore, the blood of this covenant not only secures God’s equipping us to do his will, but also secures God working in us to make that equipping successful.
The will of God is not just written on stone or paper as a means of grace. It is worked in us. And the effect is: We feel and think and act in ways more pleasing to God.
We are still commanded to use the equipment he gives: “Work out your own salvation with fear and trembling.” But more importantly we are told why: “For it is God who works in you, both to will and to work for his good pleasure” (Philippians 2:12–13).
If we are able to please God — if we do his good pleasure — it is because the blood-bought grace of God has moved from mere equipping to omnipotent transforming.
– John Piper