Eliza writes to ask,
You say the Bible in the OT says “do” and the NT says “done”. True, but some Puritan said that the false gospel is “do this and live” and the true gospel is “live and do this”.
Once we are saved we will “do”, for we were created in Christ Jesus for good works. Would you agree? (I know the stuff we subsequently do is only by God’s help and grace, but we do “do”– out of thankfulness, not for merit).
To be clear, what I said is “the law says ‘do’ and the gospel says ‘done.” The law and the gospel are found throughout the bible. This is a common misunderstanding so I’m glad you gave me an opportunity to clear it up.
The gospel is found throughout God’s Word from Genesis to Malachi. Every time God’s Word announces that salvation will be accomplished (Gen 3:15; Gen 15, Gen 17 etc) that is a reflection of or an announcement of the gospel. The prologue to the law given at Sinai is an announcement of the gospel: “I am the Lord your God who brought you out of Egypt…” In Exodus 14 when the Lord promises to deliver the church out of Egypt, that’s gospel.
In the same way, the law is found throughout the NT. Our Lord himself preached the law repeatedly. When he said, “Do this and you will live” (Luke 10:28) he was preaching the law.
When Protestants speak of “the law” and “the gospel” in this way we’re speaking about what grammarians call a “mood” of speech. The law is in the imperative mood. The gospel is in the “indicative” mood. To add a layer of complication there are imperatives connected to the gospel so not every imperative is law but we also don’t want to turn faith into a work. You can read more about this here and here To add another layer, it is true that Protestants sometimes have spoken about the OT generally as law and the NT generally as gospel insofar as there is proportionately more law under the OT and there is proportionately more gospel revealed in the NT. When our writers have spoken thus they are usually speaking about the progressive accomplishment and revelation of redemption. It was promised in the OT and fulfilled in the NT.
As to your second question, in Reformed circles we speak about the “third use of the law.” So yes, as you say, we have been redeemed by grace alone, through faith alone, in Christ alone in order that we might be sanctified by grace alone, through faith alone, in Christ alone. The power of sanctification is never the law (i.e. the command: “love God and love neighbor”). The law is like a set of railroad tracks. The tracks provide no power for the train but the train must stay on the tracks in order to function. To go off the tracks is to break the law, which is sin, but the law always remains law. It only says, “obey God, love neighbor.” It never gives any power to do what it commands. Only the gospel has power, as it were, to move the train.
Through the gospel the Holy Spirit makes us alive, gives us faith, unites us to Christ, and makes us truly thankful. By grace alone we live in thankful obedience to God’s law, we die to self and live to Christ, we sin and confess our sin, we daily repent of it (turn away), and embrace Christ and seek to be conformed more and more to his image by grace alone, through faith alone, in Christ alone, in union with Christ, by the power and presence of the Spirit.