On the outset, law seems bad. Gospel seems good. Both ought to go hand-in-hand. Both are good; or the outcome ought to be good.
Example: John says, “every tree that does not produce good fruit will be cut down and thrown into the fire” (Lk. 3:9). Then he continues talking about how the Messiah will clean up the threshing area, gather the wheat into his barn but burn the chaff with a fire that never ends (Lk. 3:17).
Sounds kind of bad…but it’s actually good. The law is kind of like a mirror. It reveals the bad in our lives, but the gospel is like fire. It burns away the bad.
Together, both law and gospel bring about a change of heart in a person. It changes a person’s heart from the inside out because the law is used to bring conviction to our hearts and our lives. But the gospel is our salvation; it saves us from the wild fire that can burn uncontrollably.
Then the message of the gospel, or good news, brings a renewal and it heals us inside after we see what the power of sin has done to our lives. The law causes us to see ourselves as we really are. The gospel gives us a way out from what we’ve become.