John Calvin Commentary Isaiah 30:13

"therefore this iniquity shall be to you as a breach ready to fall, swelling out in a high wall, whose breaking cometh suddenly in an instant." — Isaiah 30:13 (ASV)

Therefore shall your iniquity be like a breach falling. This is a threat of punishment, and Isaiah expresses it by a very appropriate metaphor. He compares wicked men to a wall that is cracked or that bulges out.

Just as the “swelling out” of a wall threatens its ruin because it cannot stand unless all its parts adhere closely to each other, so the haughtiness and insolence of wicked men are a sign and a very sure proof of their approaching ruin. This is because the more they are puffed up and swollen without any solid substance, the more readily they hurl themselves headlong, and it is impossible for them not to fall quickly by their own weight.

“Rise up,” he says, “and act insolently against God; He will quickly put down your presumption and insolence, for it is merely an empty swelling.”

From this we learn that nothing is better for us than to submit completely to God and to govern all our senses, so as to remain chained and bound by His authority. For those who exalt themselves by casting off all humility destroy themselves by collecting much wind. For a time, indeed, the Lord permits wicked men to swell and utter their big words, so that eventually, by their “swelling” and idle boasting, they may bring ruin and destruction upon themselves.