1 sn Since the author states that Cain…was of the evil one (ἐκ τοῦ πονηροῦ, ek tou ponhrou), in the immediate context this imagery serves as an illustration of 3:8a: The person who practices sin is of the devil (ἐκ τοῦ διαβόλου, ek tou diabolou). This is similar to John 8:44, where Jesus told his opponents “you people are from your father the devil…[who] was a murderer from the beginning.” In both Jewish and early Christian writings Cain is a model for those who deliberately disbelieve; Testament of Benjamin 7:5 looks forward to the punishment of those who “are like Cain in the envy and hatred of brothers.” It is not difficult to see why the author of 1 John used Cain here as a model for the opponents in light of their failure to “love the brothers” (see 1 John 3:17).
2 tn For the Greek verb σφάζω (sfazw) L&N 20.72 states, “to slaughter, either animals or persons; in contexts referring to persons, the implication is of violence and mercilessness – ‘to slaughter, to kill.’” As a reflection of this nuance, the translation “brutally murdered” has been used.
3 tn See note on the phrase “fellow Christian” in 2:9.
4 sn Everyone who hates his fellow Christian is a murderer. On one level it is easy to see how the author could say this; the person who hates his brother is one and the same with the person who murders his brother. Behind the usage here, however, is John 8:44, the only other occurrence of the Greek word translated murderer (ἀνθρωποκτόνος, anqrwpoktonos) in the NT, where the devil is described as a “murderer from the beginning.” John 8:44 refers to the devil’s role in bringing death to Adam and Eve, but even more to his involvement (not directly mentioned in the Genesis account, but elaborated in the intertestamental literature, especially the writings of Philo) in Cain’s murder of his brother Abel. This was the first incident of murder in human history and also the first outward demonstration of the full implications of sin’s entry into the world. Ultimately, then, the devil is behind murder, just as he was behind Cain’s murder of Abel. When the hater kills, he shows himself to be a child of the devil (cf. 1 John 3:10). Once again, conduct is the clue to paternity.
5 tn The verb μένω (menw) in 3:15 refers to a spiritual reality (eternal life) which in this case does not reside in the person in question. To speak in terms of eternal life not “residing” in such an individual is not to imply that at some time in the past this person did possess eternal life and subsequently lost it, however. The previous verse (3:14) makes it clear that the individual under discussion here has “remained” in death (the realm of spiritual death) and so has never possessed eternal life to begin with, no matter what he may have claimed. Taken together with the use of μένω in 3:14, the use here implies that the opponents have “remained” in death all along, and have not ever been genuine believers. Thus “residing” rather than “remaining” is used as the translation for μένουσαν (menousan) here.