In the book "Do Hard Things: A Teenage Rebellion Against Low Expectations" by Alex & Brett Harris, the authors call Christians, especially young Christian "teenagers" to action. They believe we can and should be impacting our world for Christ and they introduced this passage of Scripture as Jesus' illustration of what this God-honoring, world-changing counterculture should look like.
Although salt was used to flavor food during the Roman era, its primary use was as a preservative. In a world without refrigerators or deep freezers, a little salt rubbed into meat would slow decay. So when Jesus tells us we are "the salt of the earth," He's saying we have been placed here to preserve it until He returns -- to fight against the decay of sin, to combat sickness and suffering, and to oppose corruption and injustice.
What about light? In the Bible, light is often used to represent truth, especially the truth God has revealed in His Word. The picture of us as a city on a hill or a lamp on a stand means that as Christians we display the truth in word and action -- shining the light of God's Word and the gospel all around us, in every corner.
Putting the ideas of salt and light together gives countercultural rebelutionaries a clear mission statement: we are change makers who influence our world both as salt and light. That is to say, we influence our world both by fighting against sin, suffering, and decay and by fighting for truth and justice.
While I really appreciate the balance of what they're saying, my focus went straight to the phrase "fighting against the decay of sin." The decay of sin. Decay is such a graphic word, isn't it? Can't you just visualize the science experiment there? (On one side, rotten meat without salt... on the other side, preserved meat with salt.) I knew that salt was used as a preservative, but thinking about our responsibility in that light is such a strong mental picture for me. The world is sinful. It's decaying. It's literally rotting away in its sin. That's not so hard to believe, is it? We can look back through history and see the moral decline. ("Moral decline" sounds SO much nicer than "decaying effects of sin," but that's really what we're talking about.)
J.C. Ryle says this about verse 13:
Now salt has a peculiar taste of its own, utterly unlike anything else. When mingled with other substances it preserves them from corruption; it imparts a portion of its taste to everything it is mixed with.
So, going back to the salt/meat analogy, we (Christians, the salt) are supposed to surround the meat (the world) and protect it from the damaging effects of decay (sin). That means I'm supposed to keep the world around me from rotting in its sinfulness. But to do that, I have to actually touch the meat. Putting the salt shaker next to the meat isn't going to impart any of its benefits to the meat. I have to touch people's lives. I have to "get my hands dirty," so to speak.
That's where the "light" part comes in - trying to show God's love through our lives. Some days, our light is as strong as a beacon in a lighthouse... other days it's a tiny flickering ember. But even the smallest flicker of light can be seen in darkness.
Thank You, God, that You choose to shine Your light through me at all. I pray that I would be more than a flickering ember but would let Your light so shine through my life that the world will see and glorify You.