In Genesis 9:12, this signifies a sign of the presence of the Lord in charity. (Arcana Coelestia 1038)

In the Word, “light” in the highest sense represents Divine Truth: knowledge, ideas, understanding that come to us from the Lord. In lesser degrees -- the light of a lamp, the light of the moon and so forth -- it represents lower levels of truth, ideas and understanding drawn from more earthly sources. Also, the sun in the Word represents the Lord, with its heat representing the divine love and its light representing the divine wisdom. That wisdom flows into our minds and enters our lives in the form of truth -- things we can know and ponder that lead us and help us to be good people. This connection between light and thought is one of many spiritual/natural relationships that's embedded in our common language. People “see the light” when they understand something; we try to “shed some light” by bringing new thoughts to a difficult question; people are “enlightened” when they get new information or a more complete understanding of something. And a light bulb in a cartoon represents an idea!