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.
Numbers 15:3-10
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and will make an offering by fire to Yahweh, a burnt offering, or a sacrifice, to accomplish a vow, or as a freewill offering, or in your set feasts, to make a pleasant aroma to Yahweh, of the herd, or of the flock;
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then he who offers his offering shall offer to Yahweh a meal offering of a tenth part [of an ephah] of fine flour mixed with the fourth part of a hin of oil:
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and wine for the drink offering, the fourth part of a hin, you shall prepare with the burnt offering, or for the sacrifice, for each lamb.
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"'Or for a ram, you shall prepare for a meal offering two tenth parts [of an ephah] of fine flour mixed with the third part of a hin of oil:
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and for the drink offering you shall offer the third part of a hin of wine, of a pleasant aroma to Yahweh.
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When you prepare a bull for a burnt offering, or for a sacrifice, to accomplish a vow, or for peace offerings to Yahweh;
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then shall he offer with the bull a meal offering of three tenth parts [of an ephah] of fine flour mixed with half a hin of oil:
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and you shall offer for the drink offering half a hin of wine, for an offering made by fire, of a pleasant aroma to Yahweh.
