5:13 “You are the salt of the earth; but if salt has lost its taste, how can its saltiness be restored? It is no longer good for anything, but is thrown out and trampled under foot.
5:14 “You are the light of the world. A city built on a hill cannot be hid.
5:15 No one after lighting a lamp puts it under the bushel basket, but on the lampstand, and it gives light to all in the house.
5:16 In the same way, let your light shine before others, so that they may see your good works and give glory to your Father in heaven.
5:17 “Do not think that I have come to abolish the law or the prophets; I have come not to abolish but to fulfill.
5:18 For truly I tell you, until heaven and earth pass away, not one letter, not one stroke of a letter, will pass from the law until all is accomplished.
5:19 Therefore, whoever breaks one of the least of these commandments, and teaches others to do the same, will be called least in the kingdom of heaven; but whoever does them and teaches them will be called great in the kingdom of heaven.
5:20 For I tell you, unless your righteousness exceeds that of the scribes and Pharisees, you will never enter the kingdom of heaven.”
Salt and light have two different roles yet they have the same affect. One brings a richness in making something taste good and the other makes things more visible and clear. As Christians our job is to take on both and to make sure that nothing ever contaminates our role to spread the Gospel message. Furthermore, in spreading the Gospel, we are to strive to bring all the Glory to God. Through Him alone can we accomplish His work.
When Jesus came to this world, His teaching is what became and still is the ultimate authority. In verses 17-18 He is stating that He has come to fulfill, clarify, add to wider scale what the Law states about God and Jesus Christ. He is the full living and breathing fulfillment of the law and used His time on earth to be the ultimate teacher and example of the Gospel.
We are to learn and pursue that same example that He set for us. Preach the Gospel with Jesus Christ at the forefront of it all and trust that He will use our roles as the salt and light to proclaim His love to the rest of the world.