Editor’s note: The purpose of this series is to walk our readers through the Sermon on the Mount in Matthew 5-7 in order to help them understand what it teaches and how to apply it to our lives. This is our first such series here at Servants of Grace through an extended biblical passage and is part of our larger commitment to help Christians learn to read, interpret, reflect, and apply the Bible to their own lives.

  • Dave opened the series by looking at Matthew 5:1-3.
  • In the second post in this series, Dave explored Matthew 5:4.
  • In the third post in this series, Zach looked at Matthew 5:5.
  • In the fourth post in this series, Jason looked at Matthew 5:6.
  • In the fifth post in this series, Dave looked at Matthew 5:7.
  • Dave looked at Matthew 5:8.
  • Dave looked at Matthew 5:9.
  • Jason looked at Matthew 5:10-12.
  • Today Dave writes on Matthew 5:13-16.

SermonOnTheMountMatthew 5:13-16, “You are the salt of the earth, but if salt has lost its taste, how shall its saltiness be restored? It is no longer good for anything except to be thrown out and trampled under people’s feet. 14 “You are the light of the world. A city set on a hill cannot be hidden. 15 Nor do people light a lamp and put it under a basket, but on a stand, and it gives light to all in the house. 16 In the same way, let your light shine before others, so that they may see your good works and give glory to your Father who is in heaven.”

Jesus’ band of disciples may be persecuted, but the results of faithfulness are often happier. Disciples can change the world. We may become its salt and light. Today, we use salt as a condiment to enhance the flavor of meat and vegetables. But in the days before refrigeration and chemical preservatives, people used salt primarily to prevent the decay of meat. Similarly, the presence of a morally strong disciple can retard moral decay in society. For example, someone may refrain from telling a lewd or demeaning joke in the presence of a disciple. Our reputation for moral probity lets us function like bank auditors. Bank employees who might be inclined to embezzle money rarely attempt to do so, because they know that the auditors will catch them. Similarly, men with evil plans may abandon them simply because they know that a righteous disciple will resist them. We live in a pragmatic society. Its moral standards are low and changeable and subject to improvisation. But a salty disciple doesn’t improvise. Like salt, we are stable and unchanging.

Sodium chloride, common table salt, is a stable chemical compound, so we may wonder what Jesus means when he speaks of salt losing its saltiness (Matt. 5:13). To grasp his point, we need to understand that in ancient times “salt” was a piece of rock dug from the ground and containing many impurities. Water could wash through it, dissolving the sodium chloride and leaving a residue that looked like a salt rock and even retained its original shape, yet lacked the flavor of salt.

Jesus says, “Have salt in yourselves” (Mark 9:50), which means that we must retain our distinctive flavor. We must preserve the distinction between disciples and the world. The church is alien, so that it suffers persecution, and it is influential, so that it retards decay. The more we sense and accept our difference from the world, the greater our influence will be. The more we allow the secular society to affect us, morally, and spiritually, the more we lose our saltiness.

If the only visible difference between Christians and secular people is that we go to church on Sunday and give money away more regularly, why would they want to join us? If we divorce, alienate our children, tell lies, and make dirty deals like everyone else, why not play golf on Sunday and spend our money on exotic vacations?

Light and Praise

Jesus says, “I am the light of the world” (John 8:12). He is “a light for the nations,” to bring God’s salvation to the end of the earth (Isa. 49:6 ESV). Here Jesus tells His followers, “You are the light of the world” (Matt. 5:14). A disciple hopes to become like His master, to bless the world. “If we walk in the light, as he is in the light” (1 John 1:7 ESV), we are the light of the world.

As with salt, Jesus warns us about losing our efficacy as light. Just as “a city on a hill cannot be hidden” (Matt. 5:14), so the light of a disciple cannot and should not be hidden. In the days before electric lights, it would have been absurd to light an oil lamp and then cover it up (Matthew 5:15).

After warning us against losing our influence, Jesus tells us how to retain it: “Let your light shine before men, that they may see your good deeds” (5:16). “Good deeds” are practical acts of kindness and neighborly love. A virtuous life gives light to all around us.

It is impossible to gaze directly at the sun, high in the sky; it is painful even to try. But we gaze happily at a full moon. On a clear night, many will admire its beauty. We often forget that the moon only reflects the greater light of the sun. Somewhat similarly, many people find it difficult to gaze directly at God. Prayer, Bible reading, and meditation are too much for them. But they will observe Christians as they reflect the greater light of Jesus.

Then sometimes God sends grace—call it epistemological grace—to help His people see things as they truly are. Then men and women manifest the fourth and best response to a righteous disciple. They “see your good deeds” as the result of God’s work, and so they “praise your Father in heaven” (5:16). When they see our light, they will realize that there must be a source for our goodness, and conclude that God is that source. They will praise God for His work in and through us.


So then, there are four possible responses to a disciple’s faithful life. At the extremes are persecution and praise of God. Between them, we can serve as salt and light. Jesus says we are different, and therefore we are accountable to act like it. Let us accept the responsibility to be the light of the world. Let us not fail due to laziness, compromise, or fear. Let us act boldly and speak freely, leaving the results to God.

We all live under a common curse, because of sin. We all live under common grace from God. The common curse means that Christians do foolish things, like everyone else, and so we face opposition, for our folly as well as for our faith. But there is also common grace, so that unbelievers will listen to what we say, watch how we live, and sometimes even admire it. That grace may become uncommon, if people look beyond our goodness to its source, the goodness of God. May our light and God’s grace so shine that we will not fear opposition. May many praise God for the good that they see in us and so turn to the Lord and gain eternal life in Him.

The first sixteen verses of Matthew 5 constitute the overture to the Sermon on the Mount. In these verses, Jesus describes the character of a disciple and the results that we can expect when a disciple enters a world that operates by different standards. The Sermon on the Mount is not essentially a body of laws, yet in the next section, Jesus does describe the laws and principles that guide the behavior of a disciple, so that we can be the salt and light that this world needs.