Luke 3:9 And now also the axe is laid to the root of the trees; every tree therefore which bringeth not forth good fruit is hewn down, and cast into the fire.
This is a promise of sanctification. God promises make us holy. Jesus is our sanctification. God declares us holy and grants us His righteousness when we believe in Jesus. The Holy Spirit then comes to live in the heart and begin the sanctifying process of making our life and behavior closer to the holiness we have been given. He promises to make us better people; as we also pray in the Lord’s Prayer.
However, the process to getting there is not pleasant. We don’t want the fruitless parts of our life to be cut down and burned. We don’t want the vine branches to be pruned, taken away, and burned. We don’t want the furnace heat to be turned up to refine us. We don’t want the discipline that is necessary to yield the peaceful fruit of righteousness. But God loves us so much He won’t just let us go on with fruitless and sinful living.
Therefore, the promise through John is that the axe is laid to the root of the trees. He is already taking aim at the spot that cutting down. Trust the promise: when “bad things happen” our God will work out all things together for good. Let Him.