That is John's call. The kingdom of heaven is going to invade your world. The mood is urgent. If we don't do it, we'll be sorry. But law has its limits.
Legalism never makes it.
We cannot do it on our own, no matter how good we are or try to be. So the law is not worthy to carry the sandals of the gospel who is to come. Jesus comes with the Spirit to baptize us with the Holy Spirit and fire. And yet, the gospel is not lawless. The law must be preached, but in such a way that finally, like John, it points away from itself to Christ.