The rainbow symbolizes God’s covenant, glory — the radiance of his, beauty, holiness, and perfection.
I have set my bow in the cloud, and it shall be a sign of the covenant between me and the earth. When I bring clouds over the earth and the bow is seen in the clouds, I will remember my covenant that is between me and you and every living creature of all flesh. And the waters shall never again become a flood to destroy all flesh. (Gen. 9:13-15)
Like the appearance of the bow that is in the cloud on the day of rain, so was the appearance of the brightness all around. Such was the appearance of the likeness of the glory of the Lord. And when I saw it, I fell on my face. (Ezekiel 1:28)
And he who sat there had the appearance of jasper and carnelian, and around the throne was a rainbow that had the appearance of an emerald. (Revelation 4:3)
Then I saw another mighty angel coming down from heaven, wrapped in a cloud, with a rainbow over his head, and his face was like the sun, and his legs like pillars of fire. (Revelation 10:1)