'Grass' is natural truth, and 'flower of the field' is spiritual truth, as in Isaiah 40:5, 6. Green grass, in the Word, signifies the good and truth of the church, and of faith, which first springs up in the natural man. This is also signified by 'herb in the field.' Grass and the pulse of the herb, as in Psalm 32:2, signify what is most vile. Grass signifies science from a spiritual origin, or that by which spiritual truth is confirmed. 'Reeds and rushes' signify science from a sensory origin, or the things which confirm the fallacies of the senses, as in Isaiah 25:7. This science, considered in itself, is only a part of the lowest natural degree, which may be justly called material and bodily, in which there is little or no life. Green grass also signifies that which is alive with man. 'Grass burnt up' signifies the things which are dead in him. Grass signifies the scientific principle. Just as green grass serves animals for support, spiritual truth serves men for spiritual nourishment.

(Reference: Apocalypse Explained 507)

126. Light and Warmth in Heaven

People who think solely on the basis of nature cannot grasp the fact that there is light in the heavens; yet in the heavens there is so much light that it is vastly greater than noonday light on earth. I have seen it often, even during our evenings and nights. At first I was amazed when I heard angels saying that our world's light was nothing but shadow in comparison to heaven's light, but now that I have seen it, I myself can bear witness. Its brightness and brilliance are beyond description. What I have seen in heaven I have seen in that light, and therefore more clearly and distinctly than what I have seen in this world.