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 sunís 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 Godís 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.
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Smith, William, Dr. "Entry for 'Rainbow,'". "Smith's Bible Dictionary".