John Calvin Commentary Psalms 119:3

"Yea, they do no unrighteousness; They walk in his ways." — Psalms 119:3 (ASV)

Surely they do not work iniquity. The statement that those who follow God as their guide do not work iniquity may seem to be a mere commonplace and universally admitted truth. The prophet has two reasons for making it: first, to teach us that our life must be entirely under the direction of God; and second, that we may more diligently and carefully attend to His doctrine.

It is acknowledged by everyone that those who render obedience to God are in no danger of going astray, and yet everyone is found turning aside to his own ways. Does not such licentiousness or presumption palpably demonstrate that they have a greater regard for their own devices than for the unerring law of God?

And after all, whenever a person happens to fall, is not the plea of inadvertence instantly alleged, as if no one ever sinned knowingly and voluntarily, or as if the law of God, which is an antidote to all delinquencies because it keeps all our vicious propensities in check, did not provide us with sufficient wisdom to put us on our guard?

The prophet, therefore, very justly declares that those who are instructed in the law of God cannot set up the plea of ignorance when they fall into sin, since they are willfully blind. If they were to attend carefully to God’s voice, they would be well fortified against all the snares of Satan.

To strike them with terror, he informs them in the fourth verse that God demands a rigid observance of the law, from which it may be gathered that He will not allow its contemners to escape with impunity. Besides, by speaking to God in the second person, the prophet places Him before our eyes as a Judge.