What does the rainbow mean in the Bible?

The sign in Genesis 9

The flood is over and Noah has built an altar. Now God makes a covenant, the first one the Bible spells out in full, and it is not with Noah alone. It includes “every living creature that is with you: the birds, the livestock, and every animal of the earth” (9:10). Its terms fit in a sentence: never again a flood to destroy the earth (9:11). Then comes the sign.

I set my rainbow in the cloud, and it will be a sign of a covenant between me and the earth.

Qeshet, a warrior’s bow

Biblical Hebrew has no special word for a rainbow. It says qeshet, the word for the bow of a hunter or a soldier. Isaac sends Esau out with “your quiver and your bow” (Genesis 27:3). When the prophets picture God at war, they give him the same weapon: “He has bent his bow like an enemy” (Lamentations 2:4), and “You uncovered your bow” (Habakkuk 3:9).

That makes the picture in Genesis 9 striking. After the storm, God hangs his bow in the clouds. Many readers add that its curve faces up, away from the earth, like a weapon laid down. Babylon’s creation poem, Enuma Elish, also puts a bow in the sky: after defeating Tiamat, the god Marduk sees his bow set in the heavens as a star (tablet VI). The Babylonian flood story chooses a different token, a goddess’s lapis lazuli necklace (the parallels with Gilgamesh).

A reminder for God

When I bring a cloud over the earth, that the rainbow will be seen in the cloud, I will remember my covenant, which is between me and you and every living creature of all flesh, and the waters will no more become a flood to destroy all flesh.

The surprise is who needs reminding. The rainbow is not mainly for people to look at. God says he will look at it: “I will look at it, that I may remember the everlasting covenant” (9:16). In Hebrew, to remember is to act, and the same verb turned the flood around a chapter earlier, when “God remembered Noah” (8:1).

Rainbows elsewhere in the Bible

• Ezekiel. The prophet sees the glory of God shining “as the appearance of the rainbow that is in the cloud in the day of rain,” and falls on his face (Ezekiel 1:28).
• Revelation. A rainbow circles God’s throne, “like an emerald to look at” (Revelation 4:3), and a mighty angel comes down from the sky, clothed with a cloud: “A rainbow was on his head” (10:1).
• Sirach. A wisdom book in the Catholic and Orthodox Bibles says, “Look at the rainbow, and praise him who made it” (Sirach 43:11).

A blessing, a caution and seven colors

Jewish tradition has a blessing for the moment a rainbow appears: blessed are you, Lord our God, who remembers the covenant, is faithful to his covenant and keeps his word (Berakhot 59a). Some rabbis warned against staring at it, since Ezekiel compared it to the glory of God (Hagigah 16a). Medieval commentators asked whether there were rainbows before the flood. Nachmanides said yes: the rainbow is a natural effect of sun and rain, and what changed after the flood was its meaning.

One thing the Bible never does is count its colors. The famous seven, red to violet, come from Isaac Newton, who named seven in his Opticks (1704), matching them to the notes of a musical scale.