What does Proverbs 30:21 mean?

Agur (Proverbs 30:1) once again uses the poetic "number plus one" structure for his teaching (Proverbs 30:15, 18, 24, 29). This is a technique used often in the Bible (Proverbs 6:16; Job 5:19; Amos 1:3). He implies that these four items are disruptive: they are said to shake the earth. Poetically, this implies the people of a land, more so than the physical terrain itself. The deliberate exaggeration shows the seriousness of the concerns. All four issues (Proverbs 30:22–23) involve instability caused by something being moved out of its "proper" place. The implication is not that the persons—a slave, a fool, an unloved woman, and a female servant—are destined for their roles and should never improve them. Rather, the point is that suddenly transposing an unqualified person to authority brings unwanted consequences.

Next come descriptions of these four situations which cause people to tremble and collapse. In any era, people are troubled by perilous situations that seem to threaten stability. No one is comfortable in a civilization on the verge of collapse. Both the northern kingdom of Israel and the southern kingdom of Judah eventually collapsed under invasions by Assyria and Babylonia.