Charles Ellicott Commentary Psalms 130:3

"If thou, Jehovah, shouldest mark iniquities, O Lord, who could stand?" — Psalms 130:3 (ASV)

If you. —The word rendered “mark” is “watch” in Psalms 130:6. If “Jah” were to watch for men’s lapses, as one watches for the dawn, nothing but conspicuous punishment could follow. So Job (Job 10:14; Job 14:16) actually believed God did watch; while the prophets Jeremiah (Jeremiah 3:5) and Amos (Amos 1:11) use the word to describe the strict vigilance ensuring that consequences followed sin. It is a fact worthy of attention, that misfortune provokes at this crisis, in this people so profoundly religious, not murmurings against the Divine dealings, but a sense of deep contrition.