Albert Barnes Commentary Proverbs 30:21

"For three things the earth doth tremble, And for four, [which] it cannot bear:" — Proverbs 30:21 (ASV)

For four which it cannot bear - Better: four it cannot bear. Here the common element is that of being intolerable, and the four examples are divided equally between the two sexes. Each has its examples of power and prosperity misused because they fall to the lot of those who have no training for them, and are therefore in the wrong place.