You are the light of the world. A city set on a hill cannot be hidden; nor does anyone light a lamp and put it under a basket, but on the lampstand, and it gives light to all who are in the house. Let your light shine before men in such a way that they may see your good works, and glorify your father who is in heaven. (Matthew 5:14-16)

With those words (from the Sermon on the Mount), Christ set forth an evangelistic standard for His disciples, and all who would follow their legacy of faith. The Lord had previously called believers to function as salt in this corrupt and decaying world, preserving it from fully succumbing to the ruin of its sin (Matthew 5:13).

But in the verses above, Christ also charged His followers with the solemn duty to illuminate, shining the light of His Word in a world dominated by spiritual blindness. As John MacArthur explains, what Christ has called us to is a comprehensive gospel ministry.

Whereas salt is hidden, light is obvious. Salt works secretly, while light works openly. Salt works from within, light from without. Salt is more the indirect influence of the gospel, while light is more its direct communication. Salt works primarily through our living, while light works primarily through what we teach and preach. Salt is largely negative. It can retard corruption, but it cannot change corruption into incorruption. Light is more positive. It not only reveals what is wrong and false but helps produce what is righteous and true.^[1] John MacArthur, The MacArthur New Testament Commentary: Matthew 1-7 (Chicago: Moody Press, 1985), 244.

As we saw last time, Christians can’t faithfully function as salt in the world if their lives are marked by corruption and sinful compromise. Purity is paramount if we hope to have a preserving effect in society.

The same is true if we’re going to live lives that bring light into this sin-darkened culture. We must “be blameless and innocent, children of God above reproach in the midst of a crooked and perverse generation, among whom [we are to] appear as lights in the world” (Philippians 2:15). In fact, to function as light is essentially to reflect the character of God and His Word to the watching world.

“God is light,” John reminds us, “and in Him there is no darkness at all. If we say that we have fellowship with Him and yet walk in the darkness, we lie and do not practice the truth; but if we walk in the light as He Himself is in the light, we have fellowship with one another, and the blood of Jesus His Son cleanses us from all sin” (1 John 1:5–7). Light is not given simply to have but to live by. “Thy word is a lamp to my feet, and a light to my path,” the psalmist tells us (Psalm 119:105). God’s light is to walk by and to live by. In its fullest sense, God’s light is the full revelation of His Word-the written Word of Scripture and the living Word of Jesus Christ.

God’s people are to proclaim God’s light in a world engulfed in darkness, just as their Lord came “to shine upon those who sit in darkness and the shadow of death” (Luke 1:79). Christ is the true light, and we are His reflections. He is the Sun, and we are His moons. . . . God sheds His light on the world through those who have received His light through Jesus Christ.^[2]The MacArthur New Testament Commentary: Matthew 1-7, 244.

In the Sermon on the Mount, Christ described how His light is intended to shine through us—not as some feeble, distant speck on the horizon, but like “a city set on a hill [which] cannot be hidden” (Matthew 5:14).

By its nature and by definition light must be visible in order to illuminate. Christians must be more than the largely indirect influence of salt; they must also be the direct and noticeable instruments of light.

Both in the daytime and at night, “a city set on a hill cannot be hidden”. It is exposed for all to see. By day its houses and buildings stand out on the landscape, and at night the many lights shining out of its windows make it impossible to miss. A secret Christian is as incongruous as a hidden light. Lights are to illuminate, not to be hidden; to be displayed, not to be covered. Christians are to be both subtle salt and conspicuous light.^[3]The MacArthur New Testament Commentary: Matthew 1-7, 245.

There is nothing timid or guarded about the light that believers are to bring into the world. It’s not faint or fading, but bold and bright. And while it ought to go without saying, we must never withhold from others the light God has so richly blessed us with. Christ Himself pointed out the foolishness and futility of trying to hide the light of the gospel. “Nor does anyone light a lamp and put it under a basket, but on the lampstand, and it gives light to all who are in the house” (Matthew 5:15).

As John MacArthur explains, there is no excuse for withholding the light of God’s Word from a world in desperate need of it. “Whether we hide our light because of fear of offending others, because of indifference and lovelessness, or because of anything else, we demonstrate unfaithfulness to the Lord.”^[4]The MacArthur New Testament Commentary: Matthew 1-7, 246.

Instead, we’re instructed to “Let your light shine before men in such a way that they may see your good works, and glorify your Father who is in heaven” (Matthew 5:16).

To see good works by us is to see Christ in us. That is why Jesus says, “let your light shine.” It is not something we create or make up, but something we allow the Lord to do through us. It is God’s light; our choice is whether to hide it or let it shine.

The purpose of letting our light shine and reveal our good works is not to bring attention or praise to ourselves but to God. Our intent should be that, in what we are and in what we do, others may see God in order that they may “glorify [our] Father who is in heaven.” . . . Our good works are to magnify God’s grace and power. This is the supreme calling of life: glorifying God. Everything we do is to cause others to give praise to the God who is the source of all that is good.^[5]The MacArthur New Testament Commentary: Matthew 1-7, 246.

Put simply, the way we live ought to prompt others to glorify God. He is the source of the light in our lives, and the pattern of our lives ought to point people back to Him.