 When you see a rainbow, at least if you attended Sunday school as a child, you probably learned it's intended to remind you of a promise. God will never again send a flood to destroy the earth. Rainbows happen once in a while, but people see the sun most every day, and that also is tied to a promise. Psalm 89, God says, "'Once for all, I have sworn by my holiness, and I will not lie to David.'"