He declared in Matthew 5:13 - "You are the salt of the earth; but if the salt loses is flavor, how shall it be seasoned? It is then good for nothing but to be thrown out and trampled underfoot by men."
Jesus metaphorically referred to His followers as "the salt of the earth." What exactly does this mean? In order to fully comprehend the Messiah's statement, one must be aware of some qualities that salt possesses.
(1) Salt is a flavoring agent. This is perhaps the most commonly recognized use of salt. Who hasn't used salt to improve the taste of food that is otherwise bland?
(2) Salt is a preserving agent. Salt that is added to fresh meat will act as a preservative; it will help delay the decay process. The practice of salting meats has been used for ages.
(3) Salt increases thirst. One of my favorite soups is cheese soup. However, after consuming several bowls of the delicious soup, my body will crave fluids for the rest of the evening! The salt contained in the cheese noticeably increases my thirst.
(4) Salt melts ice. During winter months, many people use various mixtures of salt to melt ice on roads, driveways, and sidewalks.
(5) Salt irritates. Have you ever been working outside under the hot sun and had sweat run into your eyes? It stings, doesn't it? The salt contained in sweat is an irritant.
(6) Salt has destructive power. A few years ago, we had to replace certain portions of the sidewalk at the church building due to concrete damage that had been caused by heavy salting over many winters. Salt is certainly powerful stuff. Using a little bit will melt the ice, but using a lot can ruin your sidewalk! Too much salt will also harm or kill living things, such as grass, slugs, etc.
Admittedly, although we understand these attributes and usages of salt today, it is likely that the major thrust of Jesus' point pertained to salt as a flavoring agent (note His use of the word "seasoned" in the verse). One who is striving to follow Jesus will make the world a better place in much the same way that salt helps certain foods taste better. For instance, in Acts 2:47 the disciples were described as "praising God and having favor with all the people." Without a doubt, they added something good to society.
It is possible for salt to lose its flavor. Normally this should not happen, but it will if the salt becomes contaminated with impurities (e.g., dirt). Jesus is issuing a warning here. A disciple can lose the qualities that make him valuable before God as "salt" if he is not careful to remain separate from harmful impurities like sin (II Cor. 6:17). If a Christian becomes contaminated with impurity, then he is "good for nothing" in service to the Lord--at least not until he comes back to Him and seeks forgiveness on God's terms. A Christian ought to be pure and kind in thoughts, deeds, and speech (cf. Col. 4:6). Such a one will have a preserving affect on righteousness and godliness, as salt preserves food and helps prevent spoiling. He will endeavor, as salt, to remove (or melt) any hindrances that could cause others who are searching for Christ to stumble. However, in the process, he, like salt, may irritate some. Though this is not his purpose, when one lives for God and stands up for His cause, some will undoubtedly be rubbed the wrong way. It is also true that followers of the Lord, like salt, have the potential to cause destruction if they come in contact with the wrong things--namely, sin. Christians should endeavor to destroy sin from their lives. They should be a force against evil. Finally, a faithful disciple should also cause others to thirst for righteousness (cf. Matt. 5:6), as salt itself causes physical thirst.
What about you, friend? Are you the salt of the earth? Does your life manifest these qualities we've considered, or have you become contaminated with sin?