6:20–35 A call to avoid adultery because it costs so much
We return to the familiar form of the sermon, with its opening call to attentiveness (20–21) and associated promises (22–23). These pass imperceptibly into urging to avoid adultery, by being wary of enticing words and of attractive looks (24–25; see on 2:16–19; 5). There follows a long account of the reasons for that, which occupies the bulk of this section (26–35)...[A]n affair is simply not worth it.
The point is made by means of three comparisons. First, you can compare having an affair with going to see a prostitute—rather an insult to someone with a romantic view of their affair (26). It may be that the woman is being called a whore (though she is not literally that) or it may be that she is being unfavourably compared with a whore (!), since she costs much more; everything, in fact. Secondly, having an affair is like playing with fire; you will not escape getting burned (27–29). The verses play on the fact that in Hebrew fire and wife are very similar. Thirdly, having an affair is like theft (30–35): taking something that belongs to someone else because you are starving. With ordinary theft you pay the penalty; all the more with stealing someone’s wife. The ‘property’ view of marriage is taken for granted here, because that was how people thought of the matter, though the strength of the husband’s reaction perhaps implies the feeling that adultery involves more than interference with his property. Carson, D. A., France, R. T., Motyer, J. A., & Wenham, G. J. (Eds.). (1994). New Bible commentary: 21st century edition (4th ed., p. 591). Leicester, England; Downers Grove, IL: Inter-Varsity Press.