Once Jesus had assured His obedient disciples that they were indeed among the transformed and blessed people who were destined to inherit the kingdom of heaven, He raised a word of caution. Unlike so many modern preachers who continually assure spiritual goats that they could never forfeit the salvation they supposedly possess, Jesus loved His true disciples enough to warn them that they could indeed remove themselves from the category of the blessed.
You are the salt of the earth; but if the salt has become tasteless, how can it be made salty again? It is no longer good for anything, except to be thrown out and trampled under foot by men. 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 (Matt. 5:13-16).
Notice that Jesus didn’t exhort His disciples to become salt or become light. He said (metaphorically) they already were salt, and He exhorted them to remain salty. He said (metaphorically) that they already were light, and exhorted them not to let their light be hidden, but to continue shining. How this stands in contrast to the many sermons given to “Christians” of their need to become salt and light. If people aren’t already salt and light, they aren’t Christ’s disciples. They aren’t among the blessed. They aren’t going to heaven.
In Jesus’ time, salt was used primarily as a preservative of meats. As obedient followers of Christ, we are what preserves this sinful world from becoming completely rotten and corrupt. But if we become like the world in our behavior, we are truly “no longer good for anything” (v. 13). Jesus warned the blessed to remain salty, preserving their unique characteristics. They must remain distinct from the world around them, lest they become “unsalty,” deserving to be “thrown out and trampled under foot.” This is one of many clear warnings against backsliding directed at true believers that is found in the New Testament. If salt is truly salt, it is salty. Likewise, followers of Jesus act like followers of Jesus, otherwise they aren’t followers of Jesus, even if they once were.
Christ’s true followers are also the light of the world. Light always shines. If it isn’t shining, it isn’t light. In this analogy, light represents our good works (see Matt. 5:16). Jesus wasn’t exhorting those who have no works to drum some up, but exhorting those who have good works not to hide their goodness from others. By so doing, they would glorify their heavenly Father because His work in them is the source of their goodness. Here we see a beautiful balance of God’s gracious work and our cooperation with Him; both are needed for anyone to be holy.
