4:8-15 Malice in the heart ends in murder by the hands. Cain slew Abel, his own brother, his own mother's son, whom he ought to have loved; his younger brother, whom he ought to have protected; a good brother, who had never done him any wrong. What fatal effects were these of our first parents' sin, and how must their hearts have been filled with anguish! Observe the pride, unbelief, and impenitence of Cain. He denies the crime, as if he could conceal it from God. He tries to cover a deliberate murder with a deliberate lie. Murder is a crying sin. Blood calls for blood, the blood of the murdered for the blood of the murderer. Who knows the extent and weight of a Divine curse, how far it reaches, how deep it pierces? Only in Christ are believers saved from it, and inherit the blessing. Cain was cursed from the earth. He found his punishment there where he chose his portion, and set his heart. Every creature is to us what God makes it, a comfort or a cross, a blessing or a curse. The wickedness of the wicked brings a curse upon all they do, and all they have. Cain complains not of his sin, but of his punishment. It shows great hardness of heart to be more concerned about our sufferings than our sins. God has wise and holy ends in prolonging the lives even of very wicked men. It is in vain to inquire what was the mark set upon Cain. It was doubtless known, both as a brand of infamy on Cain, and a token from God that they should not kill him. Abel, being dead, yet speaketh. He tells the heinous guilt of murder, and warns us to stifle the first risings of wrath, and teaches us that persecution must be expected by the righteous. Also, that there is a future state, and an eternal recompence to be enjoyed, through faith in Christ and his atoning sacrifice. And he tells us the excellency of faith in the atoning sacrifice and blood of the Lamb of God. Cain slew his brother, because his own works were evil, and his brother's righteous, 1Jo 3:12. In consequence of the enmity put between the Seed of the woman and the seed of the serpent, the war broke out, which has been waged ever since. In this war we are all concerned, none are neuter; our Captain has declared, He that is not with me is against me. Let us decidedly, yet in meekness, support the cause of truth and righteousness against Satan.

15. whosoever slayeth Cain—By a special act of divine forbearance, the life of Cain was to be spared in the then small state of the human race.

set a mark—not any visible mark or brand on his forehead, but some sign or token of assurance that his life would be preserved. This sign is thought by the best writers to have been a wild ferocity of aspect that rendered him an object of universal horror and avoidance.