The Witness of Counter-Cultural Living - Matthew 5:13-16
Jesus begins the Sermon on the Mount with a list of attributes that are found in those who are part of the kingdom of God along with related blessings. What’s clear from that list is that those who live as citizens of God’s kingdom live counter-cultural lives – lives that are very different from the world around them.
Following ‘the Beatitudes’ Jesus continues to drive home the point that the people of God will stand out in the world – but this is part of His plan. We are in the world, and our presence is meant to impact the world. Using two metaphors Jesus teaches us how our lives in the world serve to restrain evil and provide a witness to the goodness and glory of God.
D.A. Carson says it this way: The norms of the kingdom, worked out in the lives of the heirs of the kingdom, constitute the witness of the kingdom.
Christians are Salt (For a world that’s decaying) (5:13)
- Thinking about salt – Salt has several uses, but the primary use, especially in the first century, was as a preservative. Salt is used to slow down the process of rot and decay.
- What the metaphor says about the world – Ever since the fall mankind has been given to sin and the end of sin is death. Our world is marked by the decay and rot of sin.
- What the metaphor says about the Christian in the world – While the world is marked by things like pride, jealousy, anger and division, God has set apart a people marked by humility, purity, righteousness and peace. When Jesus calls the people of God the salt of the earth, He is communicating that by our very presence – we are being used by God to slow the rot and decay of the world.
- Salt must be salty – The people of God are meant to be a witness to the world of the salvation and glory of God, but if we aren’t living according to God’s ways then our witness is muted. If we as Christians begin to live and blend in with the world around us – then we’re like salt without the properties of salt that make it effective (1 Pt. 2:9–12).
Christians are Light (For a world of darkness) (5:14-15)
- What the metaphor says about the world – Throughout the Scriptures we have the imagery of the world being in darkness. Without God the world and those in the world are in complete and total darkness – without any light of truth or hope.
- What the Bible says about light in the darkness
- Jesus as the light (John 1:9, 4-5; 8:12)
- Jesus transfers us from darkness to light (Ephesians 5:8)
- What the metaphor says about the Christian in the world – When Jesus calls the people of God the light of the world, He is making it clear that it’s through us that the world can see the goodness and glory of God. As light in the darkness the people of God should stand out and serve as a witness to the world of the glory and salvation of God.
- Light cannot and should not hidden – Using the imagery of a city on a hill and a lamp in a room Jesus makes the point that light cannot and should not be hidden. In the same way the people of God who are living His way will be seen and we should be careful not to diminish the light.
The Christian life as a witness (5:16)
- The command – Jesus carries on with the metaphor but now adds a command. As the people of God we must let our light shine. We let our light shine when we live and speak as the people of God.
- The reason – As we live God’s way in the world people will see our good works. The goal, however, is not to be seen (Matthew 6:1), but that the world will see the goodness and glory of God and turn to Him for salvation (1 Peter 2:10-12).
Summary - Perhaps we can sum it all up this way. The true Christian cannot be hidden, he cannot escape notice. A man truly living and functioning as a Christian will stand out. He will be like salt; he will be like a city set upon a hill, a candle set upon a candlestand. But we can also add this further word. The true Christian does not even desire to hide his light. He sees how ridiculous it is to claim to be a Christian and yet deliberately to try to hide the fact. A man who truly realizes what it means to be a Christian, who realizes all that the grace of God has meant to him and done for him, and understands that ultimately, God has done this in order that he may influence others, is a man who cannot conceal it. 
 D.A. Carson, Jesus’s Sermon on the Mount and His Confrontation of the World, A Study of Matthew 5-7, Baker Books, 1987, 2018, pg. 39.
 David Martyn Lloyd-Jones, Studies in the Sermon on the Mount, Martino Publishing 2011 (1959), pg. 174