Not as Cain, who was of that wicked one, and slew his brother. And wherefore slew he him? Because his own works were evil, and his brother’s righteous. (1 John 3:12)
In these words we have an inspired commentary on the scene depicted in Gen. 4:1-15. John looks under the surface of events and sees the real cause for Cain’s hatred and jealousy of Abel in the contrast between the “works,” or actions, of the two brothers (cf. on Heb. 11:4). Actions, resulting from men’s thoughts, serve as an indication of character, and it would appear that Cain revealed his true nature before the crowning act of murder. There was no fault in Abel that excused or explained the horrible deed. Abel’s humble obedience to God aroused his brother’s jealous hatred. Abel’s only offense was righteousness. Cain’s conscience condemned his own way of life, and he saw himself faced with the choice of acknowledging his sin or destroying Abel, who made him so aware of his own sinfulness (PP 74). So also did the leaders of the Jews drive themselves into condemning Jesus to die.
Wherefore?
Literally, “on account of what?” With this question John stimulates his readers to examine the motivation behind Cain’s murder of Abel and introduces an explanation for the world’s hatred of the Christian (v. 13).
Slew.
Gr. sphazō, “to slaughter,”“to butcher,”“to slay.” The word occurs in the NT only here and in the Revelation (chs. 5:6; 6:4; etc.).
Of that wicked one.
Cain proved himself to be a child of the devil, even as a Christian may prove himself to be a child of God (cf. on v. 10).
Cain.
This is the only direct reference in this epistle to an OT incident. John sets forth Cain as the supreme example of lack of brotherly love. It may be noticed that the historicity of Cain’s murder of Abel is not called in question: the apostle accepts the Genesis narrative as genuine and analyzes the causes of Cain’s deed (see on Gen. 4:8-15).