Genesis 9:13 - Coke's Commentary on the Holy Bible

I do set my bow in the cloud— If the covenant, as we suppose, had a two-fold reference, the bow was also a two-fold sign; and its temporal or natural respect must then, and ought now, to remind us of its much more important spiritual and gracious design. God hath always been pleased to appoint some outward and visible sign of the inward and spiritual grace conferred by his covenants with man: thus, circumcision was appointed to Abraham, &c.