There are several approaches to the OT Brit found in the Keshet in Parshat Noah. (B'raishit: 8: 21-22)
- The more "mystically" inclined will read that Hashem created the rainbow just to signify the Covenant. They will think the rainbow a brand new phenomena.
- The more "rationally" minded will think that while rainbows had long predated Noah. Hashem was only now investing the Rainbow with new meaning and new significance through the covenant.