Charles H. Spurgeon on Psalms 129:4

The LORD is righteous: he hath cut asunder the cords of the wicked; i.e., he has put an end to their domination and tyranny over us. In the Hebrew word which is rendered "cords" there is a reference to the harness with which the oxen were fastened to the plough; and so to the involved machinations and cruelties of the enemy. The Hebrew word properly denotes thick twisted cords;figuratively, intertwined wickedness; Mic 7:8. "The cords of the wicked", therefore, signify their power, dominion, tyranny, wickedness, and violence. These cords God is said "to have cut", so that he should have made an end; and, therefore "to have cut" for ever, so that they should never be reunited. —Hermann Venema.