Oil
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.
Ezekiel 43:7
7
He said to me, Son of man, [this is] the place of my throne, and the place of the soles of my feet, where I will dwell in the midst of the children of Israel forever. The house of Israel shall no more defile my holy name, neither they, nor their kings, by their prostitution, and by the dead bodies of their kings [in] their high places;
