A couple weeks ago, the largest wildfire in California history ravaged the northern part of the state. I learned to appreciate the magnitude and impact of wildfires when my family lived in southern California for a little over four years. The fire’s size, speed, and impact are stunning. Even more amazing are the men and women who put themselves in harm's way to fight them.

A tension must be maintained when fighting a wildfire. Firefighters have to get close enough to the fire to be able to "fight" it, while maintaining a safe enough distance to avoid the danger of the blaze. That tension can be instructive for believers. It’s not unlike the task God has for believers. They must influence the culture, while avoiding the explicit and implicit dangers that are part of life in a fallen world.

There's a target space for believers somewhere between assimilating to the culture and influencing nonbelievers for the sake of the gospel. This has always been a challenge for Christ followers. The friction is baked into our lives by nature of our calling in the world.

To manage this tension, Christians have always depended on certain biblical images. Perhaps no biblical metaphors have guided believer’s relationship to the culture more than the salt and light metaphors of Matthew 5:13-16. Yet, it’s often difficult to pinpoint exactly what Jesus was calling His followers to in these verses. People have found justification for all sorts of activities in these metaphors, including evangelism, political action, art, and feeding the poor.

I’d like to revisit these important metaphors and help you understand and apply them to this ever-present tension in your life. To do this, I will go back to the biblical text and utilize two basic Bible study tools to shed light on the meaning of both salt and light.


Context is King, Queen, and the entire royal family when it comes to Bible study. The meaning of the text can't be known apart from its context. If this is true, then we can't begin to grasp the point of the salt and light metaphors without broadening our reading out to at least the near context. Of course, these metaphors come fairly close to the beginning of the Sermon on the Mount, which covers Matthew 5-7. The Sermon on the Mount is a work of art. The structure is breathtaking. Where the salt and light metaphors are situated within the sermon sheds light on their meaning and importance.

The sermon has three major parts. The main body begins in 5:17 and goes to 7:12 and is bookended by the phrase “law and the prophets.” Jesus situates this sermon, and His entire ministry, as the fulfillment of the story of Israel in the OT. The major theme of the sermon, I’m convinced, is the righteousness of Jesus’s kingdom citizens which leads to human flourishing. He develops this theme from three distinct angles in the body. First, in 5:17-48 Jesus speaks to transformative righteousness. His followers will recognize the true intent of the law as they move from legality to wholeness, grounded in love. Second, in 6:1-21, Jesus shows how a heart shaped by genuine righteousness practices its religion in three ways that are distinct from hypocrites. Third, in 6:19-7:12, Jesus turns his disciple’s attention outward so they can live out a social righteousness in how they relate to the material world and others.

After the main body, Jesus brings the Sermon to a conclusion with three images that drive home his point. With these words, he is showing kingdom citizens how to live out what they heard, how to display the righteousness He has defined in the Sermon. He speaks of two gates (vv. 13-14), two trees (vv. 15-23), and two houses (vv. 24-27). Those who hear this Sermon cannot ride the fence. They must actively put into practice what they have heard.

I’ve intentionally kept the sermon’s introduction till third because that is where we find the salt and light metaphors. The introduction comes in two parts. Verses 3-12 give us nine macarisms, each beginning with the Greek word makarios, that paint a counter-cultural picture of a life well lived. These 9 qualities are virtues that characterize citizens of God’s kingdom. Then, in verses 13-16, Jesus defines His kingdom followers as salt and light.

To properly understand the salt and light metaphors we need to grasp the overall theme of the Sermon and recognize these metaphors form the second half of the introduction. Here’s the point: you cannot make sense of what it means to be salt and light unless you see these metaphors as vitally connected to the Beatitudes and the overall theme of righteousness. If the Beatitudes are the qualities that define righteousness in kingdom citizens, then to be salt and light means that these virtues must shape how you live in the world. You can see this in verse 16. It says people are supposed to see the good works of those who are light. Those who embody the way of being articulated in verses 3-12 are salt and light.

Analogy of Faith

The London Baptist Confession describes this important tool for interpretation like this: “The infallible rule of interpretation of Scripture is the Scripture itself; and therefore when there is a question about the true and full sense of any Scripture (which are not many, but one), it must be searched by other places that speak more clearly.” (1.9)

Clearly, we can’t rightly understand the metaphors of salt and light by thinking about how we use salt and benefit from light in this cultural moment. We have to understand how these images are used in Scripture. Of the two metaphors, salt is the more difficult to connect with other passages of Scripture. This is probably because the Bible uses salt in a variety of ways. A helpful article by Andrew Wilson at The Gospel Coalition lists five of these purposes in the ancient world.

And yet, it’s possible to bring the majority of the ways the Bible speaks of salt together under one heading.

“(1) As ‘salt,’ the disciples exhibit covenant fidelity and so preserve the continuance of the covenant. This category includes the probability that Jesus’ followers are conceived of as sacrifices in their own persons. (2) By virtue of their identification as salt, the disciples share in covenant fellowship, including that of the table, and thus form a society in communion with the covenant Lord. (3) The disciples impart purity to the creation, thereby causing it to be better than before—a new creation. (4) There is the punitive function of salt. If the world rejects the message of the disciples, their witness to the blessings of salvation turns into a condemnation of it.”[i]

Salt is most often and most clearly used in a covenantal context to signify the reality and presence of a covenant. So, when Jesus calls his kingdom disciples the salt of the earth, he is saying their presence in the world indicates the existence and perpetuity of God’s covenant.

In other words, the disciple’s presence in the world, living out the Beatitudes and the realities of the sermon, show God's desire for the nations to come to him and embrace the covenant He is offering.

While the metaphor of light receives a longer treatment by Jesus (vv. 14-16), and seems to be clearer, I think we too often fail to let Scripture guide our understanding of how Jesus uses the image of light. A few verses earlier, in Matthew 4:12-17, Jesus’s preaching ministry is introduced. When he arrives on the scene, he fulfills an OT expectation found in Isaiah 9:1-2. Twice in this passage the promised true Davidic King is called the light.

If you were to stop your study of the image of light in the book of Isaiah with Isaiah 9, you would be left wondering if there’s any connection to Jesus’s use of this metaphor to describe His followers. It’s no coincidence that Matthew put these two occurrences of “light” so close together in his book.

Jesus was so influenced and shaped by the Old Testament that He utilizes language from the Hebrew Scriptures more than we often realize. The navigation program on my phone has my work and home addresses permanently set at the top for easy access. Perhaps we should read the NT with our home addresses set to navigate our study back through the pages of the OT, particularly when we are reading Jesus. Far too often our journey toward the authorial intent of the passage bypasses the Bible Jesus knew and used during His earthly ministry.

So, what does the book of Isaiah reveal concerning the meaning of this image of light? As we’ve seen, the future Davidic king is called the light in Isaiah 9. As you move forward to the First Servant Song in Isaiah 42, you find God speaking to His servant and saying that He will give Him “as a covenant for the people, a light for the nations.” This passage connects God’s covenant with His servant’s role as a light for the people. Isaiah 49:6 and 51:4 continue to describe the work of the servant of God as a covenantal light for the nations, but when you reach Isaiah 58 there’s a subtle shift in the language used. Now, instead of directly associating the spreading light with an individual, it will emanate from the people. In Isaiah 58:8 it is the light of the people that will break forth, and this illumination to others will be associated with their healing. Verse 10 describes their light going forth as they do good works such as feeding the hungry and helping the afflicted.

Finally, Isaiah’s theology of light culminates in chapter 60 when the future restoration of Israel is described. Israel’s final destiny brings together both the individual servant’s light shining on Israel as well as Israel’s light going forth to the nations. Isaiah 60:1 commands the people of Israel to arise and shine precisely because the glory of the Lord has risen upon them. Verse 2 indicates that the Lord will arise upon them and that His glory will be seen upon them. Then verse 3 brings the original mission of Israel into focus as “the nations shall come to your light, and kings to the brightness of your rising.”

So, when Jesus uses this language of light in Matthew 5:14-16 to describe the mission of His followers, He’s saying He fulfills these servant songs and His followers take up this mission to extend God’s glory to the nations.

Both salt and light present kingdom citizens, who are living out the Beatitudes, as covenantal representatives of Christ.

The implications of this are far reaching. Understanding the main point of these metaphors pushes us beyond the simple application of influence or evangelism to more clearly fleshing out our role as covenantal representatives by the way we live in the world.

[i] Don B Garlington, “‘The Salt of the Earth’ in Covenantal Perspective,” Journal of the Evangelical Theological Society 54, no. 4 (December 2011): 748.