(NLT) “13You are the salt of the earth. But what good is salt if it has lost its flavor? Can you make it salty again? It will be thrown out and trampled underfoot as worthless. 14You are the light of the world—like a city on a hilltop that cannot be hidden. 15No one lights a lamp and then puts it under a basket. Instead, a lamp is placed on a stand, where it gives light to everyone in the house. 16In the same way, let your good deeds shine out for all to see, so that everyone will praise your heavenly Father.”
Jesus uses the imagery of salt and light to illustrate the kingdom living that comes from following the beattitudes. Salt played a critical role in the ancient world. The word "salary" comes from the word for salt as soldiers were sometimes paid their wages in salt. Because of its worth there were unscrupulous trades in "fool’s salt," substances that appeared the same as this vital, crystaline substance, but had none of the benefits. Salt functioned as a preservative. It provided a necessary mineral to the diet. It also provided flavor to food, in addition to other uses. It appears from the text that the function of salt to enhance the taste of food may be what Jesus has in mind. Either that or the means for testing the worth of your salt was tasting. “What good is salt if it has lost its flavor? Can you make it salty again?” If you had purchased “fake” salt in the marketplace, there was nothing you could do about it. Fool’s salt was simply tossed out as useless.
As salt played a critical role in the daily life for those during the time of Christ, light also played a critical role, especially in terms of safety. For travelers, the lights of the cities provided crticial navigational tools. If a traveler completed a journey after sunset, the primary orientation was the lights of the cities. Almost all cities in the ancient world sat on “hilltops” as a protection against attack. Based on the topology of the land, the lights of the cities could be seen for miles around, functioning as a directional map. Light was also critical in daily activities. Lamps in houses functioned much the same way for a household as city lights functioned for the traveler. The reason a person would light a lamp was to provide assistance to everyone in the house. The burning lamp provided the necessary illumination for someone to walk safely from one place to another within an otherwise dark house.
Disciples of Jesus were to be salt and light. In other words, the life of a disciple should function as spiritually essential elements to the life and safety of their culture. How then, do the disciples of Jesus Christ exhibit the attributes of salt and light? The basis of a disciple’s saltiness and the source of the disciple’s light is good works. "In the same way..." meaning, in the same way that salt and light impact everyone around so the disciples life should impact everyone around. "In the same way, let your good deeds shine out for all to see." Good works provides the medium for disciples to be salt and light. Paul says it this way in Ephesians 2:10, "For we are His workmanship, created in Christ Jesus for good works, which God prepared beforehand so that we would walk in them." Believers in Christ Jesus have been made for the sake of doing good works. God created us with good works in mind. God created us with the intent that good works would play a continuous and significant role in our lives because we are to "walk in them."
The danger comes from the internal heart issues surrounding disciples when good works are involved. The motive for a disciple's good deeds is God's glory. “In this way, let your good deeds shine for all to see, so that everyone will praise your heavenly Father.” The phrase, "so that," speaks volumes to the risk of good works without proper motive. We are to do good works with the praise of God our Father constantly on our minds. Juxtapose this idea with the words of Jesus about those giving, praying and fasting in the very next chapter of Matthew 6. In Chapter 6, Jesus chastises self-glorifying religious works. "Beware of practicing your righteousness before men to be noticed by them; otherwise you have no reward with your Father who is in heaven." Two distinctives appear between chapter 5 and chapter 6 in Matthew's Gospel. First, the type of good works in mind in chapter 5 seem to be the types of actions found in the beatitudes, such as humility, mercy, peacemaking, pursing righteousness, and bearing testimony to Christ. In chapter 6, the works are all outward, religious activities, giving, praying and fasting. The second distinctive when contrasting chapter 5 and 6 comes from the motive of the individual. In chapter 5, the motive is the praise of God. Chapter 6 identifies the motive of giving, praying and fasting that produces no benefit, praise of self. God’s glory must drive our motivation for performing good works. We do not seek glory for ourselves if we are to be salt and light. We do not seek glory for the good works themselves, if we are truly functioning as salt and light. Instead, salt and light in the disciple’s life materialize when the good works direct others to the glory of God, “so that everyone will praise your heavenly Father.”