Shared ground
Job 18:20–21 closes Bildad’s speech by turning the wicked person’s collapse into a public lesson. The ruin is not private or forgettable: it becomes “his day,” a remembered moment that later hearers find shocking and earlier witnesses find terrifying. Bildad then states a general rule: this is what happens to the “dwellings” and “place” of the unrighteous, the person who does not “know” God.
These verses explicitly link moral identity (“unrighteous,” “doesn’t know God”) with a household’s final condition (ruined dwelling) and with how the community talks about it (astonishment and fear).
Where interpretation differs (only where needed)
What “his day” means. Some read “his day” as the day of death. Others read it as the day disaster overtook him (which may include death but focuses on collapse and judgment-like reversal). Both fit Bildad’s theme of a decisive downfall that becomes a warning story.
Who the “after” and “before” people are. Some take them as people across time: later generations (“after”) and earlier observers (“before”). Others see a directional contrast (e.g., west/east or “those behind/those in front”), emphasizing the breadth of public reaction rather than a timeline.
What it means to “know God.” Some hear “know” mainly as having a real relationship with God (not merely information). Others understand it as refusing to acknowledge God in a practical, lived way. Either way, Bildad ties godlessness to the fate of the home.
Why the disagreement exists
The Hebrew wording allows more than one natural sense for “day” and for the “after/before” contrast, and “know” can describe both relational knowledge and acknowledged allegiance. The poem also speaks in compressed, proverb-like statements, which leaves room for different but overlapping readings.
What this passage clearly contributes
Bildad’s closing verdict presents the wicked person’s end as a recognizable pattern: it becomes a story that produces dread and amazement, and it is summarized as the typical outcome for the unrighteous household. Within the book’s larger debate, this strengthens Bildad’s insistence that suffering and collapse reliably reveal moral and spiritual failure, stated here in terms of “not knowing” God (cf. Job 18:20).