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.

9914. 'And its hole shall have a border round about' means that it is bounded and enclosed on every side. This is clear from the meaning of 'a border', or edging, around the hole or opening on the upper part of the robe, as being bounded and enclosed on every side; for that border or edging which went all round served to bound and enclose. The words here and those following immediately after describe the course which the inflow of celestial good into spiritual good takes. What is involved in this inflow is similar to the course taken by the forces flowing from a person's head through the neck into the body, as is clear from what has been stated regarding correspondence in the paragraph immediately above.

[2] The nature of this influx must also be stated briefly. All the chief things that belong to the head, that is to say, to the cerebrum and cerebellum, are assembled into bundles of fibres and tiny nerves there, and so assembled pass down through the neck into the body. Within the body they spread out in every direction and move its parts altogether as the will, which begins in the brain, desires. Similar to all this is the flow of powers and forces down from the celestial kingdom, which is the head in the Grand Man or heaven, into the spiritual kingdom, which is so to speak the body there. This inflowing is also what is meant and described by 'the robe's hole for the head in the middle', and the limits of it by 'a border round about'. This then is why a boundary and enclosure on every side is meant by 'the border' which that hole possessed. The actual boundary is described next.