Genesis 9:12

And God said, This is the token of the covenant which I make between me and you and every living creature that is with you, for perpetual generations:

Cross-reference

In Genesis 17:11, circumcision is also a sign of the covenant—parallel to the rainbow as a covenant sign here.

In Exodus 12:13, the blood on doorposts is a sign of deliverance—similar to the rainbow as a sign of God's covenant promise here.

In Exodus 13:16, phylacteries serve as physical signs to remember deliverance—parallel to the rainbow as a visual covenant sign here.