After the flood, God set the rainbow in the clouds as the sign of his covenant with Noah and every living creature: I do set my bow in the cloud, and it shall be for a token of a covenant. Whenever the rain returns and the bow appears, it is a promise remembered — that the waters shall no more become a flood to destroy all flesh.
There is deep meaning in the image. A bow is a weapon of war, but this bow is hung in the sky pointing away from the earth, as if God has laid down his weapon. The rainbow reappears around the throne of God in Revelation, encircling his glory with the colours of mercy. It remains a sign that after judgment comes covenant faithfulness, and that God's promises outlast every storm.
The Rainbow in Scripture
I do set my bow in the cloud, and it shall be for a token of a covenant between me and the earth.