Oil
![oil jug of oil and olives](/bundles/ncbsw/media/roberta-sorge-uOBApnN_K7w-unsplash.webp)
Oil -- typically olive oil -- symbolizes the good that comes from celestial love. Celestial love is love of the Lord, the highest and purest love we can have. The good of celestial love is the desire to be good springing from celestial love: Wanting to do the Lord's will because you love Him. That's not a state many reach, even in heaven, but it's a beautiful goal. This representation makes sense based on the idea that the sun -- the source of all natural light and heat, and thus all natural life -- represents the Lord, the source of all spiritual light, heat and life. Burning oil was the most pure fire available in Biblical times, thus the closest representation of the sun people could create.
Arcana Coelestia #2003
2003. 'As for Me, behold, My covenant is with you' means union of the Divine Essence with the Human Essence. This is clear from the meaning of 'a covenant' as conjunction, dealt with in 665, 666, 1023, 1038. Here it is the union of the Divine Essence with the Human Essence, as is evident from this meaning and from the internal sense of what has gone before, and so from the actual words 'My covenant is with you'.