See Ex. 20:5; 34:14; Deut. 4:24. The root of the word translated “jealous” means “to become intensely colored in the face,” that is, from deep emotions such as love, zeal, or anger. By His very nature God cannot be otherwise; how could He share the affections of His people with other gods (2 Cor. 6:14-17)? Light and darkness cannot exist together; to harbor darkness in the soul one must exclude the light.