“the entire Scripture of God is divided into two parts: commandments and promises.”
The commandments are law and to be obeyed. The promises are gospel and to be trusted. Confusing these categories is the fast-track towards losing the gospel.
For Luther and the reformers, the theological use of the law is to convict us of sin and guilt and to drive us to Christ. His blood alone can answer the demands and damnation of the law.
And so, for Luther (and for many even in the reformed tradition), evangelical preaching involves this journey of law and then gospel - the demands that kill and the promise of Christ that brings life.
At which point, non-Lutherans are liable to say, "That's sweet. And artificial. Are we really meant to force Scripture into this mould?" It can seem a little alien.
Now I'm not a Lutheran, certainly not in the denominational sense. But let me suggest that something like "law-gospel" is not a Procrustean bed for the Scriptures, but the natural contour God's Word.
As I argue here - it's not just Genesis 1 that can be divided into forming and then filling. The whole of the bible runs from form to its filled-full reality. The law is a key example of this. The Good Life outlined by Moses is filled full by Jesus (Matthew 5:17).
And the journey from form to filled-full reality is a journey from death to life. First comes darkness, then light. First the seed, then the plant. First the curses of exile, then the blessings of restoration. First Adam, then Christ. First the cross, then the resurrection. First the old covenant, then the new covenant. First the old earth, then the earth renewed.
In all this, the ultimate reality is known and intended in advance, but there is a journey to undergo. And law-gospel is but one expression of that journey - through death to life. Luther was by no means the first to spot this pattern. I want to argue that this is the basic preaching of the prophets. Today we'll think about Jeremiah. Tomorrow, Isaiah.
In Jeremiah 1, the prophet is called by the Appearing Word of the LORD who puts His words in Jeremiah's mouth. At this point in history, the Word of the LORD will not appear to Israel en masse (Hebrews 1:1). Christ speaks through His prophets to the people. Only in the last days does the Word of the LORD come in the flesh as His own prophet (Hebrews 1:2).
But here in Jeremiah 1, what is the shape of the proclamation which Christ commissions Jeremiah to fulfil?
9 Then the Lord reached out his hand and touched my mouth and said to me, “I have put my words in your mouth. 10 See, today I appoint you over nations and kingdoms to uproot and tear down, to destroy and overthrow, to build and to plant.” (Jeremiah 1:9-10)
Notice the pattern? Uprooting, tearing down, destroying, overthrowing. But then: building and planting.
As Jeremiah speaks to his own people he will proclaim total destruction. Exile will come. Inescapably.
Essentially, those in Jerusalem respond: "Yeah, sure. We're with you on the total destruction thing. Total destruction for the nations. But we have the temple of the LORD, the temple of the LORD, the temple of the LORD!" (Jeremiah 7:4)
But no, says Jeremiah. The temple is the first place to feel the flames. Judgement begins with the house of God (cf 1 Peter 4:17). God's people are not exempted from judgement. In fact they are judged more harshly. Doom is coming. And it is unavoidable. Your special status, special places, special rituals, special behaviours, special leaders are all worthless. The end is nigh. Your only hope is God's Leader, His Shepherd:
“The days are coming,” declares the Lord,
“when I will raise up for David a righteous Branch,
a King who will reign wisely
and do what is just and right in the land.
6 In his days Judah will be saved
and Israel will live in safety.
This is the name by which he will be called:
The Lord Our Righteousness. (Jeremiah 23:5-6)
It's law then gospel. It's Israel and all its worthless efforts then Christ and all His mighty salvation.
The whole pattern of prophetic preaching is like this. The prophets preach righteousness to the people. But they also make it clear that the people's righteousness cannot save. Exile is coming and the only hope is God's Messiah on the other side of judgement.
Law-gospel isn't a 16th century invention. It's at least 2000 years older than that.