Jesus identifies Himself with Yahweh in the Sermon on the Mount when He compares His disciples to the persecuted prophets of old (Matt. 5:11–12; Jer. 37–38). The disciples who speak for Jesus are like the prophets who spoke for the Lord of the covenant; therefore, Christ implies His divine sovereignty.
The prophets carried out their ministries in full view of the people of Israel, and so we are not surprised to see that their successors, the disciples of Jesus, do not build the kingdom of God in secret. This is the point of today’s passage. Our Savior calls His disciples the “salt of the earth” (Matt. 5:13) and the “light of the world” (v. 14), two substances that permeate and transform the food, or the darkness, in which they are found. Like salt and light, the church is to have a transformative effect on the surrounding society.
Salt is often produced as tiny grains and is not expensive given its prevalence. Yet its value far outweighs its apparent insignificance. Christians are to be like salt and have a positive impact on the culture far beyond what is expected from the powerless. The meaning of Jesus’ metaphor is probably not limited to any single benefit we get from salt, but we will highlight its preservative quality. The church must have a preserving effect on society and by its influence prevent the world from rushing headlong toward ungodliness. Christianity has fulfilled this role historically, leading the way in the advance of human rights. But take note that we are salt only if we maintain our difference from the world around us. In the Near East, salt can be found mixed with gypsum or sand, diluting its “saltiness” and worth. The same fate can befall us if we bend over backward to show the world how much we are like them (v. 13; 1 Peter 1:14–16).
Rural communities like the one Jesus addresses in Matthew 5 well know how blinding darkness can be. Yet the glow of a city in the distance can give those living in the pitch black of night a sense of direction and bearing. Just as walking around the camp at night is dangerous without a lighted torch, Jesus calls us to be the light of the world, to live as those transformed by the Spirit so that the world will take notice and be led to glorify the Father (vv. 14–16).
Christ’s call for us to be salt and light is not an impossible one. In keeping with New Testament ethics, Jesus first tells us what we are and then calls us to live up to that standard. In Him we are salt and light (Matt. 5:13–16), and so we are to live out by faith what He has made us to be. If you are discouraged by your saltlessness or darkness, remember that Jesus declares you to be salt and light and press on, knowing that by the power of the Spirit you can obey His charge.