Caused by the reflection and refraction of the rays of the sun shining on falling rain. It was appointed as a witness of the divine faithfulness (Gen. 9:12-17). It existed indeed before, but it was then constituted as a sign of the covenant. Others, however (as Delitzsch, Commentary on Pentateuch), think that it "appeared then for the first time in the vault and clouds of heaven." It is argued by those holding this opinion that the atmosphere was differently constituted before the Flood. It is referred to three other times in Scripture (Ezek. 1:27, 28; Rev. 4:1-3; 10:1). the token of the covenant which God made with Noah when he came forth from the ark that the waters should no more become a flood to destroy all flesh. The right interpretation of (Genesis 9:13) seems to be that God took the rainbow, which had hitherto been but a beautiful object shining in the heavens when the sun's rays fell on falling rain, and consecrated it as the sign of his love and the witness of his promise. Ecclus. 43:11. The rainbow is a symbol of God's faithfulness and mercy. In the "rainbow around the throne," (Revelation 4:3) is seen the symbol of hope and the bright emblem of mercy and love, all the more true as a symbol because it is reflected from the storm itself.
Rainbow