Surely they do not work iniquity The statement, that they who follow God as their guide do not work iniquity, may seem to be a mere common-place, 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, secondly, that we may more diligently and carefully attend to his doctrine. It is acknowledged by every one, that those who render obedience to God are in no danger of going astray, and yet every one 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, as often as a man happens to fall, is not the plea of inadvertence instantly alleged, as if none 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 furnish us with sufficient wisdom to put us upon 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, seeing they are willfully blind. Were they 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 suffer the contemners of it to escape with impunity. Besides, by speaking to God in the second person, he places him before our eyes as a Judge.

They also do no iniquity - See the notes at 1-John 3:9. The meaning is, that they are righteous; their character is that they do that which is right. It cannot mean that all persons who are religious are actually and absolutely perfect - for no man would hold this opinion; no one does hold it. It is general language such as is commonly used to describe an upright or righteous man. The declaration is true of all who are the friends of God - or, who are truly; religious - in the following senses:
(1) That they are habitually and characteristically righteous;
(2) That they intend to do right - for a man who deliberately purposes to do wrong - to lead a life of sin and disobedience, cannot be a pious man.
(3) That when they do err, it is not the result of intention, or the design of their life, but because they are tempted; are overcome with passion; are led by the power of their native corruption of heart to act contrary to their better judgment and their true character.
See Romans 7:14-17. On the other hand, it is true that a man who is not characteristically righteous; who is not an upright man in his dealings; who is not true, and honest, and temperate, and just, and benevolent, cannot be a child of God and heir of heaven. No exactness of orthodoxy, and no fervour of emotion, and no zeal in the cause of religion, can constitute true piety without this.
They walk in his ways - Habitually; constantly; characteristically. They are not merely honest, upright, and just in their dealings with men, but they walk in the ways of God; they are religious.

They also do no iniquity - They avoid all idolatry, injustice, and wrong; and they walk in God's ways, not in those ways to which an evil heart might entice them, nor those in which the thoughtless and the profligate tread.

They also do (b) no iniquity: they walk in his ways.
(b) For they are ruled by God's Spirit and embrace no doctrine but his.

They also do no iniquity,.... Not that they are free from indwelling sin, nor from the acts of sin, nor that what they do are not sins; but they do not make a trade of sinning, it is not the course of their lives; nor do they do iniquity with that ease and pleasure, without reluctance and remorse, as others do: or rather as new creatures, as born again, they do not and cannot commit sin; for the new man is pure, spiritual, and holy; and nothing can come out of that, or be done by it, which is the contrary. This is a distinct I from the old man, or corrupt nature, to which all the actions of sin are to be ascribed; see 1-John 3:9;
they walk in his ways; in the ways of God and Christ, into which they are guided and directed, and where they are kept, and in which they find both pleasure and profit. Here end the descriptive characters of good and happy men.

his ways--the course He reveals as right.