“Under three things the earth trembles; under four it cannot bear up: a slave when he becomes king, and a fool when he is filled with food; an unloved woman when she gets a husband, and a maidservant when she displaces her mistress.”
The fourth and final “unbearable” situation under which the earth trembles is when a maidservant takes the place of her mistress. This verse is either referring to a circumstance where a servant woman has an affair with her master’s wife and then displaces the wife, or when a servant woman is simply elevated in influence (or authority) over the woman of the house.
Either way, it is an immoral and terribly disruptive situation.
Scripture gives an example when Abraham mistakenly followed the bad advice of Sarah in taking her maidservant, Hagar, as a wife. The motive was to have Hagar bear children to fulfill God’s promise, but this was not how the Lord intended to fulfill his promise.
This mistake and disobedience brought jealousy and conflict to an ugly level, and it extended far beyond Abraham and Sarah’s immediate situation and created constant, historic conflict between the descendants of Hagar (the Arab nations) and the descendants of Sarah (the Jewish nation). That conflict is as serious today as at any time in history. Because of it, “the earth trembles.”
And how many families have been ruined because the husband divorces his wife because of an affair with a friend or co-worker or acquaintance? The family is the foundational structure of human society, and when affairs/divorce break up the family, it is devastating for the children and society as a whole.
It is unbearable.