When it came to communicating truths about the kingdom of God, Jesus had His work cut out for Him. His time was spent traveling the Judean countryside teaching complicated and abstract truths to simple and largely uneducated people.
This is why He taught in parables so often. These basic stories were easy to understand, remember, and pass on. And when Jesus wasn’t using parables, He often taught in metaphors and similes because they were effective at communicating ideas that would have been more difficult to convey.
In the Sermon on the Mount, Jesus shocks His listeners with the Beatitudes and then launches into the metaphor of salt and light to help his listeners understand how they’re called to interact with the world.
Let’s examine the implications of the image of salt and light.
The salt of the earth
You are the salt of the earth. But if the salt loses its saltiness, how can it be made salty again? It is no longer good for anything, except to be thrown out and trampled underfoot (Matthew 5:13).
When we think of salt, we tend to think of a fairly cheap spice that we keep on the table next to our pepper. If we recall our high school science, we might remember it as the compound sodium chloride.
But that’s not how the crowd around Jesus would have thought about salt. They would have recognized its two major properties:
No one in the first century had freezers, so if you wanted to preserve meat, it had to be cured, and this was done by drying and salting it. Jesus seemed to be telling them that they were to help preserve the world where they lived.
But they were also instructed to give it flavor. Salt naturally enhances taste by intensifying certain flavors and decreasing others. Salt has the unique ability to make sweet things seem sweeter and diminish the impact of naturally bitter things.
Jesus seemed to be saying that those who were in step with God would make the world a more enjoyable place by enhancing and communicating God’s goodness. And, as Jesus pointed out, if His followers were to lose their saltiness, they would no longer be effective at protecting and amplifying God’s goodness in the world.
Light of the world
You are the light of the world. A town built on a hill cannot be hidden. Neither do people light a lamp and put it under a bowl. Instead they put it on its stand, and it gives light to everyone in the house. In the same way, let your light shine before others, that they may see your good deeds and glorify your Father in heaven (Matthew 5:14–16).
We have an understanding of light that first-century Jews didn’t. For instance, we know that it’s because of light that we can see the entire spectrum of colors. We know that sunlight provides the energy needed to sustain life on earth and gives us critical vitamin D.
But because most of us have never lived without electric light, we miss Jesus’ main point. When we walk into a dark room, we flick a switch and the room is bathed in light. But that wasn’t the case for the people Jesus addressed. They lit their homes at night with small oil lamps.
The picture of someone lighting a lamp and then putting it under a clay pot would have been humorous to this crowd. The only reason to light a lamp was so you could see, and just like Jesus suggested, you would place that lamp in a place where it could give off as much light as possible.
The implication was clear. Our faithfulness should be evident to all. The behavior of God’s people should be a light that draws others to it. Outsiders should be drawn to praise God when they see our good deeds.
The evidence of the faithful
The metaphors of salt and light specifically addressed the impact faithfulness should have in the world. It should illuminate and preserve. Like both salt and light, our relationship with God should have an obvious impact on everyone who comes in contact with it. Jesus isn’t just calling us to be devoted, He’s encouraging us to have an influence everywhere we go.