Genesis 4:1-26

Cain and Abel. The Descendants of Cain

The narrative, which forms part of the Primitive document, impressively shows how sin, having once appeared, became hereditary in the human race, and speedily developed into its most revolting form. Its details enable us to see how jealousy, when indulged, leads to hatred and murder, and violates not only the ties of humanity but those of family affection; how the sinner casts off all regard for the truth and for his natural obligations; how progress in sin adds to the misery of man's lot; and 'conscience doth make cowards of us all.' The truths taught are, that God looks on the hearts of His worshippers, seeks to restrain the sinner ere he yields to passion, marks the death of the innocent, and graciously mitigates His punishment when His mercy is sought.
The story is but loosely attached to that of Paradise. It assumes that there is already a considerable population in the world, for no explanation is given whence Cain got his wife, or who were the people whose vengeance he feared. It presupposes the institution of sacrifice, of which nothing has been said previously, and of blood revenge. Various solutions of these difficulties have been suggested, but scholars now generally suppose that the story occupied originally a later position among the traditions than that in which we find it.