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.

8877. 'On the third and on the fourth [generations]' means in a long sequence, and joined together. This is clear from the meaning of 'three' as what is complete from start to finish, dealt with in 2788, 4495, 7715, thus a long sequence, so that 'the third [generation on sons' is falsities in a long sequence (for the meaning of 'sons' as falsities, see immediately above in 8876); and from the meaning of 'four', like two, as joined together, dealt with in 1686, 5194, 8423, so that 'the third and the fourth [generations of] sons' are falsities joined together in a long sequence. This explanation of 'the third and the fourth [generations of] sons' must inevitably seem to be nonsensical or foreign to the meaning of the Word; but it should be remembered that in the internal sense numbers do not mean numbers but real things, see 482, 487, 575, 647, 648, 755, 813, 1963, 1988, 2075, 2252, 3252, 4264, 4495, 4670, 5265, 6175.