Scholars have long debated the precise nature of the “sin unto death” in 1 John 5:16-17. Commentators regularly note that certain Old Testament sins led to the death penalty (see for example, Smalley, Word Biblical Commentary, 2007), but they usually dismiss these capital sins as the Old Testament context for John’s “sin unto death.” Instead, they tend to argue that John was referring either to intentional versus unintentional sins in the Old Testament (Smalley), or to rejecting the faith in a manner similar to the opponents mentioned in 1 John 2:19 (see for example, John Painter, Sacra Pagina, 2002).
I propose that a careful look at whole of 1 John and John’s use of the Old Testament indicates that John is indeed referring to sins for which people were put to death in the Old Testament. I argue that through the use of Old Testament imagery, John is casting both the opponents of 2:19, and any of his readers who would reject that Christ had come in the flesh, as those who are violators of the Old Testament law. From his statement that those who have come to know God will keep his commandments (2:3), to his definition of sin as lawlessness (3:4), to his references to Genesis and the story of the devil (3:8-10) and his description of Cain as a murderer (3:11-13), John both casts his opponents in light of these Old Testament lawbreakers, and he warns his readers not to engage in this type of law breaking.
1 John 5:16-17 and the sin unto death then, in part at least, is John clarifying what he means by statements like “we know that everyone who has been born of God does not sin” (5:18). While John recognizes that everyone sins, John also operates in Old Testament categories, where some sins brought the penalty of death in a way that others did not. I will argue that this Old Testament context for the sin unto death makes the most sense of how John engages with the Old Testament throughout his letter.