can anyone find me the exact words of r' hirsch, when he comments that...
the rainbow is one of the many אותות such as shabbos, tefillin, and circumcision- all of which are designed to keep alive and fresh the great teachings which Hashem gave man. The rainbow is the eternal sign that no matter how bleak the future may seem, Hashem will lead mankind to its ultimate goal.
quoted from Artscroll (schottenstein edition), parshas noach 9:8-17