I'm not convinced it isn't about more life in general as per Jesus' declaration, "I am the light of the world." Granted, those that believe will have the Holy Spirit as I noticed in particular today when reading through the threads and Mark 16:16 was posted,
Whoever believes and is baptized will be saved, but whoever does not believe will be condemned.
I noted that statement was made without saying, "whoever does not believe and is not baptized will be condemned" stirring my thinking on whether believing is baptisms and indeed, the term, kai, can denote a 'namely' sense as much as it might denote an 'additional' requirement.
At any rate, I think it goes without saying that those that the moment one believes they do so in agreement with the Holy Spirit, and are at that time baptized, and I can't see anyone, once baptized with the Holy Spirit ever 'running out of oil.' I'm not intimately familiar with the miracle of the oil at Hanukkah but the widow's oil would apply.
I will let AI have a crack at defining the oil.
Scripture only
1. Oil explicitly symbolizes the Spirit of the LORD
- 1 Samuel 16:13
“Then Samuel took the horn of oil and anointed him in the midst of his brothers, and the Spirit of the LORD rushed upon David from that day forward.” - Isaiah 61:1
“The Spirit of the Lord GOD is upon me, because the LORD has anointed me…” - Zechariah 4:1–6 (lampstand supplied by oil)
“These are the two olive trees and the two lampstands…
Then he said to me, ‘This is the word of the LORD… Not by might, nor by power, but by my Spirit, says the LORD of hosts.’”
Oil → anointing → Spirit.
2. Lamps require oil to give light; light is from the LORD
- Exodus 27:20
“You shall command the people of Israel that they bring to you pure beaten olive oil for the light, that a lamp may regularly be set up to burn.” - Psalm 18:28
“For it is you who light my lamp; the LORD my God lightens my darkness.” - Proverbs 20:27
“The spirit of man is the lamp of the LORD…”
Lamp + oil → light given by God.
3. The Spirit is given, indwells, and must be possessed personally
- Ezekiel 36:26–27
“And I will give you a new heart… And I will put my Spirit within you…” - Zechariah 4:12
“What are these two olive branches… that pour out golden oil?” - Matthew 25:8–9
“The foolish said to the wise, ‘Give us some of your oil…’
But the wise answered, ‘Since there will not be enough for us and for you…’”
The oil cannot be shared, just as the Spirit is personally received.
4. The Spirit is linked with readiness and watchfulness
- Matthew 25:10
“And while they were going to buy, the bridegroom came, and those who were ready went in with him to the marriage feast…” - Romans 8:9
“Anyone who does not have the Spirit of Christ does not belong to him.” - Galatians 5:25
“If we live by the Spirit, let us also keep in step with the Spirit.”
Readiness is possession of the Spirit.
5. Absence of oil = absence of life from God
- Job 29:3
“When his lamp shone upon my head, and by his light I walked through darkness.” - Jude 12
“Clouds without water, carried along by winds; autumn trees without fruit, twice dead…”
No oil → no light → no life.
Conclusion (from Scripture)
- Oil = anointing
- Anointing = Spirit of the LORD
- Lamps without oil = profession without the Spirit
- Entrance depends on being ready, which Scripture defines as having the Spirit
Therefore, by Scripture, the oil in the lamps signifies the Holy Spirit.