Matthew 5: 13 – 16
To demonstrate the impact these people would make on their world, Jesus used two common illustrations: salt and light. Jesus’ followers would be like salt in that they would create a thirst for greater information. When one sees a unique person who possesses superior qualities in specific areas, he desires to discover why that person is different. It is also possible that salt means these people serve as a preservative against the evils of society. Whichever view one takes, the important quality to note is that salt ought to maintain its basic character. If it fails to be salty, it has lost its purpose for existence and should be discarded.
A light is meant to shine and give direction. Individuals Jesus described in verses 3–10 would obviously radiate and point others to the proper path. Their influence would be evident, like a city on a hill or a lamp … on its stand. A concealed lamp, placed under a bowl (a clay container for measuring grain) would be useless. Light-radiating people live so that others see their good deeds and give praise not to them but to their Father in heaven. (V. 16 includes the first of 15 references by Jesus in the Sermon on the Mount to God as “your [or ‘our’ or ‘My’] Father in heaven,” “your heavenly Father,” “your Father.” Also see vv. 45, 48; 6:1, 4, 6, 8–9, 14–15, 18, 26, 32; 7:11, 21. One who stands in God’s righteousness by faith in Him has an intimate spiritual relationship to Him, like that of a child to his loving father.)
Barbieri, L. A., Jr. (1985). Matthew. In J. F. Walvoord & R. B. Zuck (Eds.), The Bible Knowledge Commentary: An Exposition of the Scriptures (Vol. 2, p. 29). Wheaton, IL: Victor Books.