13 “You are the salt of the earth, but if salt has lost its taste, how shall its saltiness be restored? It is no longer good for anything except to be thrown out and trampled under people’s feet.
14 “You are the light of the world. A city set on a hill cannot be hidden.15 Nor do people light a lamp and put it under a basket, but on a stand, and it gives light to all in the house. 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 who is in heaven.
Matthew 5:13–16 ESV – Bible Gateway
Last week the lectionary covered the Beatitudes in the first part of the Sermon on the Mount, this week we continue on.
This Gospel passage is relatively short, and yet, there is so much to mine here. The hearers of the Beatitudes would have had much to think about what being a disciple of Jesus meant. Jesus here specifies that this is not just something interior to reflect on. This interior change must reflect through all your life as a witness to others. To move out of ourselves to not only absorb and live his teachings, but to lead others to give glory to God.
To an extent, we can take in some of the imagery Jesus is using here in these metaphors of salt and light. There is a dimension here that would pass by most of us if we do not understand these metaphors as related to the Old Testament.
Some commentaries I read delved into this aspect as related to the Temple and the sacrifices, but I especially liked how Dr. John Bergsma summarizes this.
In this passage about the disciples as “salt” and “light,” Jesus makes generous use of Temple imagery that goes unnoticed by most contemporary readers. The image of “salt” is related to the Temple because the priests made heavy use of salt, sprinkled on the sacrifices and elsewhere, as a symbol of purity and as a seasoning and preservative for the sacrificial meat intended for human consumption. Apparently it was also used in covenant rituals because the Chronicler speaks of the kingdom of the LORD being given to the House of David by a “covenant of salt” (2 Chr 13:5; see also Num 18:19). So salt is rich in ideas of purity, preservation, covenant fidelity, proper worship, and savor. “Salt ❲that❳ loses its taste” would be salt from which any true sodium has leached out, leaving behind only other minerals and impurities, fit only to be used for traction on roads.
“Light” was also associated with the Temple, for on the basis of prophecies like Zechariah 14:7–8, the Jews believed that in the end times, the Temple would be the source of continual light for the people of Israel. This belief was enacted each year at the great Temple feast, the Festival of Tabernacles, during which the Temple courts were lit up twenty-four hours a day by huge menorahs that had to be lit by young men on ladders. Jewish tradition describes “no shadow being in Jerusalem” during these ancient celebrations. It was during or just after this Feast of Tabernacles (John 7:2) that Jesus taught his disciples, “I am the light of the world” (John 8:12).
A “city set on a mountain” is a clear reference to the Temple city Jerusalem, the most famous “city set on a mountain” in all Israel. In fact, the ridgeline on which Jerusalem sits is one of the highest in all the traditional territory of Israel, with the result that travel to Jerusalem was typically described as “going up” (Hebrew ‘alah) to Zion, since one literally had to ascend to the city from almost any other location. The Temple, in turn, was built on the highest point of the ancient city, dominating the skyline.
Dr. Brant Pitre points out:
… the cereal offering is is a translation of the Hebrew word minchah, which literally means just a bread or a grain offering. So you had these cereal offerings that would often be offered to God in the form of a caked bread—sometimes mixed with oil—and interestingly often offered on the altar with bread and wine, so as an offering of bread and wine. So it was kind of like a meal that you would share with God. So the salt is added to the cereal offering to signify the covenant banquet between you and God. It is something that is essential for a sacrifice that is being offered to the Lord. “With all your offerings you shall offer salt,” Leviticus says. So there may be a deeper meaning going on when we go back to the Sermon on the Mount.
This helps us to see the dimension of how we pour out our life in sacrifice for the Lord. In the opening verses in Romans 12, St. Pauls writes:
12 I appeal to you therefore, brothers, by the mercies of God, to present your bodies as a living sacrifice, holy and acceptable to God, which is your spiritual worship. 2 Do not be conformed to this world, _ but be transformed by the renewal of your mind, that by testing you may discern what is the will of God, what is good and acceptable and perfect. 
St. Thomas Aquinas, in his commentary on the Gospel of Matthew, addresses the sacrificial sense and dives into the spiritual sense of salt as used here.
He says, therefore: You are the salt. He compares them to salt on account of four reasons. The first reason is on account of the production of salt, which comes from both the wind and the sun’s heat: for spiritual generation is from the water of Baptism and the power of the Holy Ghost; “Unless a man be born again of water and the Holy Ghost, he cannot enter into the kingdom of God” (Jn. 3, 5). And the production of salt comes from the heat of the sun, meaning from the fervor of love which is from the Holy Ghost; “The charity of God is poured forth in our hearts, by the Holy Ghost who is given to us” (Rom. 5, 5). Secondly, it is on account of the utilities of salt, of which the first is its use, that all things are seasoned with salt: hence, it signifies the wisdom which apostolic men ought to have; “The wisdom of doctrine is according to her name, and she is not manifest unto many, but with them to whom she is known, she continueth even to the sight of God” (Eccli. 6, 23), and, “Walk with wisdom towards them that are without, redeeming the time” (Col. 4, 5). The second use: was that in every sacrifice salt was added (Lev. 2, 13),: because apostolic teaching ought to be reflected in our every deed. The third use is that it absorbs excess moisture and by this preserves from putrefaction. In this way the Apostles were restraining carnal concupiscences by their teaching; “The time past is sufficient to have fulfilled the will of the Gentiles, for them who have walked in riotousness, lusts, excess of wine, revellings, banquetings and unlawful worshipping of idols” (I Pet. 4, 3), and, “Let us walk honestly, as in the day: not in rioting and drunkenness, not in chambering and impurities, not in contention and envy” (Rom. 13, 13). The fourth effect of salt is that it makes the ground sterile. Hence, it is said that some conquerors oversowed salt outside a city which they captured so that nothing would grow. In like manner, also the Gospel teaching makes the ground sterile, namely, so that earthly works do not spring up in us; “And have no fellowship with the unfruitful works of darkness: but rather reprove them” (Eph. 5, 11). Therefore, the Apostles are called salt because they have pungency for withdrawing from sins; “Have salt in you: and have peace among you” (Mk. 9, 49).
The Ignatius Catholic Study Bible remarks concerning verse 5:16:
“Earlier chapters make no mention of the Fatherhood of God. In the Sermon on the Mount, however, Jesus calls God “Father” a total of 17 times (chaps. 5–7). “ and “God’s Fatherhood is the deepest mystery of his identity; from eternity he fathers a divine Son (Jn 1:1), and throughout history he adopts us as his children in Christ (Jn 1:12; Gal 4:4–7).”
Two other aspects to cover are how Jesus calls us the “Light of the World” and that he is also the “Light of the World” along with us showing our good works to others instead of keeping them in secret.
First Dr. Peter Kreeft:
…Another reason these two sayings of Jesus don’t contradict each other, the sayings about letting our light shine before men and about doing our good deeds in secret, is that they are addressed to different occasions, different states of mind. When we are in danger of cowardice, Jesus tells us to let our light shine; when we are in danger of pride, he tells us to pray in secret. When we’re down on ourselves he brings us up, and when we’re up on ourselves he brings us down. Why? Because Jesus is the perfect mirror of God the Father; and God is love; and love always wills the good of the loved one; and the good of the loved one is his needs, not his wants; and his need is always to be delivered from both despair and pride, both cowardice and arrogance, both self-defeatism and self-satisfaction, both self-hate and self-love. 
And lastly Dr. Brant Pitre:
So is Jesus the light of the world or are the disciples the light of the world?” The answer is yes, it’s both, it’s both-and, it’s a classic Catholic both-and. It’s not that Jesus is the light or we are the light, it is both. The light that the disciples are going to shine in the world only comes through their union with, an imitation of, Jesus. He is the source of all of the light of the Gospel, but it is going to shine through his disciples and out into the world because of them. That’s the imagery being used here.
- The Word of the Lord: Reflections on the Sunday Mass Readings for Year A – John Bergsma
- Catholic Productions, Commentaries by Brant Pitre
- St. Thomas Aquinas, Commentary on the Gospel of St. Matthew
- English Standard Version Catholic Edition
- The Ignatius Catholic Study Bible – The New Testament
- Peter Kreeft, Food for the Soul: Reflections on the Mass Readings Cycle A
- Photo by Ben White on Unsplash
- The Word of the Lord: Reflections on the Sunday Mass Readings for Year A, John Bergsma, 5TH SUNDAY IN ORDINARY TIME ↩
- Catholic Productions, Brant Pitre. 5th Sunday in Ordinary Time (Year A) ↩
- English Standard Version Catholic Edition (2019). Augustine Institute. ↩
- Commentary on the Gospel of St. Matthew, Dolorosa Press ↩
- Ignatius Catholic Study Bible: New Testament ↩
- Peter Kreeft, Food for the Soul: Reflections on the Mass Readings Cycle A ↩
- Catholic Productions, Brant Pitre. 5th Sunday in Ordinary Time (Year A) ↩