In Exodus 3:12, this signifies a confirmation of the truth that the Divine proceeded from Himself. (Arcana Coelestia 6870)

(References: Arcana Coelestia 1039, Genesis 9:12, 9:13, 9:17)

The "midst" of something in the Bible represents the thing that is most central and most important to the spiritual state being described, the motivation that drives everything else. In general this will be something we love or feel, because at the core of things we are what we love; our loves define us.

(References: Apocalypse Revealed 44, 90, 268; Arcana Coelestia 2252, 2940, 10153, 10365, 10557, 10635, 10641)