13 “You are the salt of the earth. But if the salt loses its saltiness, how can it be made salty again? It is no longer good for anything, except to be thrown out and trampled underfoot. 14 “You are the light of the world. A town built on a hill cannot be hidden. 15 Neither do people light a lamp and put it under a bowl. Instead they put it on its stand, and it gives light to everyone in the house. 16 In the same way, let your light shine before others, that they may see your good deeds and glorify your Father in heaven.
Jesus now moves on from describing the blessed state of the believer (the beatitudes) to the positive influence they should have on all people around them (as opposed to Pharisees and others who were leading people away from the Kingdom Matthew 23:13). Most within Israel at this time were not putting on a good witness since the majority of them were unbelievers relying on the Law to be saved (had very little flavor in this case) and were, therefore, not producing as they should have been (see the parable of the unfruitful fig tree in Luke 13:6-9). That was the primary reason Jesus said these words because Israel was not nearly as salty as they should have been because most were unbelievers (even though most Israelites were supposed and assumed to be believers). However, as we will mention below, this teaching still applies to the church today in various ways.
Although Christians differ from everyone else because of their polar opposite position in Christ, they must still set a good example and share this blessed state with others so that they too, may partake of all the spiritual blessings rewarded to those who believe. The “you” at the beginning of verse thirteen can only indicate the state of born-again individuals whom the Lord expects to witness to all men through their godly thinking, speech, and behavior. And yes, this still applies to the church today.
But as to why Jesus used two illustrations to make His point was probably just for the sake of emphasizing a critical truth through repetition (and to clarify the meaning of what He said to His listening audience). I believe both “salt” and “light” refer to our general conduct in thought, speech, and action around others and our direct service to them through our spiritual gifts in the ministries God has assigned to every believer.
Not everyone is called to evangelization as their primary service to Christ. But that doesn’t excuse them from not sharing the gospel when the opportunity presents itself (whatever the situation or circumstances). However, I believe Jesus had our general conduct and direct service to others (and, therefore, to Him) in mind. We must share the goodness of the kingdom with others, a process only possible through spiritual growth, progress, and production. However, if spiritual growth is lacking (for whatever reason), the believer will inevitably become less salty, and the light of their witness will dim. This truth applies as much today as it did during our Lord’s time when He spoke these words.
So what of those who lose their saltiness and brightness? Assuming the person is an apostate (a former believer gone unbeliever), they will have no proof or evidence through their conduct or behavior that they have faith in Christ. And if they lack godliness, spiritual production resulting in fruit will also be absent.
5 For this very reason, make every effort to supplement your faith with virtue, and virtue with knowledge, 6 and knowledge with self-control, and self-control with steadfastness, and steadfastness with godliness, 7 and godliness with brotherly affection, and brotherly affection with love. 8 For if these qualities are yours and are increasing, they keep you from being ineffective or unfruitful in the knowledge of our Lord Jesus Christ. 9 For whoever lacks these qualities is so nearsighted that he is blind, having forgotten that he was cleansed from his former sins.
2 Peter 1:5-9 demonstrates that faith is the foundation of our salvation (and everything that comes after that) empowered by the grace of God. It is from this necessary quality that all other spiritual fruits of the Spirit flow because faith is what brought us into God’s family initially. None of us will ever be perfect in any of these areas and may be lacking/struggling in some of them to whatever degree. But to the one who lacks ALL of these qualities and shows no sign of possessing them, we would categorize as someone who has lost their “salty flavor” and the light of their witness. All believers will possess at least some of the spiritual qualities mentioned above, even the least spiritually mature who have and will ever live. But those who ultimately turn their back on God and revert to unbelief (for whatever reason(s)) will be cut off, just like the unfruitful branch in John fifteen mentioned below. Only those who continue to believe will be saved. Those who stop believing will demonstrate it in their life and will, therefore, not inherit the kingdom of God because of that same unbelief. The verses below could not be more straightforward.
“I am the true vine, and my Father is the gardener. 2 He cuts off every branch in me that bears no fruit, while every branch that does bear fruit he prunes so that it will be even more fruitful. 3 You are already clean because of the word I have spoken to you. 4 Remain in me, as I also remain in you. No branch can bear fruit by itself; it must remain in the vine. Neither can you bear fruit unless you remain in me. 5 “I am the vine; you are the branches. If you remain in me and I in you, you will bear much fruit; apart from me you can do nothing. 6 If you do not remain in me, you are like a branch that is thrown away and withers; such branches are picked up, thrown into the fire and burned. 7 If you remain in me and my words remain in you, ask whatever you wish, and it will be done for you. 8 This is to my Father’s glory, that you bear much fruit, showing yourselves to be my disciples.