If thou, Lord, shouldest mark iniquities - If thou shouldst observe, note, attend to, regard all the evil that I have done. The Hebrew word means properly to keep, to watch, to guard. The word, as used here, refers to that kind of vigilance or watchfulness which one is expected to manifest who is on guard; who keeps watch in a city or camp by night. The idea is, If God should thus look with a scrutinizing eye; if he should try to see all that he could see; if he should suffer nothing to escape his observation; if he should deal with us exactly as we are; if he should overlook nothing, forgive nothing, we could have no hope.
Who shall stand? - Who shall stand upright? Who could stand before thee? Who could hope to be acquitted? This implies
(1) that the petitioner was conscious of guilt, or knew that he was a sinner;
(2) that he felt there was a depth of depravity in his heart which God could see, but which he did not - as every man must be certain that there is in his own soul;
(3) that God had the power of bringing that to light if he chose to do it, so that the guilty man would be entirely overwhelmed;
(4) that he who urged the prayer rested his only hope on the fact that God would not mark iniquity; would not develop what was in him; would not judge him by what he saw in his heart; but would deal with him otherwise, and show him mercy and compassion.
Every man must feel that if God should “mark iniquity” as it is - if he should judge us as we are - we could have no hope. It is only on the ground that we may be forgiven, that we eau hope to come before him.