This Times of Israel blog post http://blogs.timesofisrael.com/bible-blog-your-lifes-story/ is based upon my book Photograph God: Creating a Spiritual Blog of Your Life http://photographgod.com.
“Make an ark of acacia wood…. Cover it with a layer of pure gold on the inside and outside” (Exodus 25:10, 11). We asked Ron, a rabbi and biologist who lives with his family in the Negev, why significant objects created for the Tabernacle were made of commonplace acacia wood coated with gold rather than pure gold. He explained that the acacia tree symbolizes the living, growing, dynamic oral Torah that engages all generations in creative dialogue. It must be joined with gold, a stable element that neither tarnishes nor rusts, symbolizing the eternal values of the written Torah. “It [Torah] is a tree of life for those who grasp it …. Its ways are ways of pleasantness and all its paths are peace” (Proverbs 3:18, 17).
Yesod/Foundation is where the spiritual world of Emanation, the cognitive world of Creation, and the affective world of Formation merge and flow together into the material world of Action. We are elevated beyond these four worlds in the blog post “Leviticus 8: Higher Than Sky” for the Torah portion Kedoshim/Holy.