I have not sat with vain men. He again declares the very great dissimilarity which existed between him and his adversaries. For the contrast is always to be observed, that wicked men, by all the harm and mischief they wrought against him, could never drive him from the path of rectitude. This verse might likewise be joined with the former, as if completing the sentence, in this way, That David, by confiding in the favor of God, had withdrawn himself from deceivers. The words, sitting and walking, denote sharing in counsel and fellowship in working, according to what is said in the first psalm. David denies that he had any intercourse with vain and deceitful men. And certainly the best remedy to recall and save us from the assembly of the wicked is to fix our eyes upon God's goodness; for he who walks in the confidence of God's protection, committing all events to his providence, will never imitate their deceitfulness. Those whom he denominates in the first clause, men of vanity, he soon after terms nlmym, naälamim, that is, close and wrapped up in craftiness. [1] For in this consists the vanity of dissimulation, that deceitful men conceal in their hearts another thing than that which their tongues declare. It is, however, absurd to derive this word from lm, alam, to play, for it is out of place here to compare their impostures to children's play. I confess, indeed, that those who give themselves to craftiness are mockers; but why have recourse to such a forced exposition, when it is plain that the word shows the source from which all lying and deceit proceed? Thus faith, which steadily looks to God's promises, is aptly opposed to all the crooked and iniquitous counsels in which unbelief involves us as often as we ascribe not proper honor to the guardianship of God. David teaches, by his own example, that we have not the slightest cause to fear that our integrity will make us a prey to the ungodly, when God promises us safety under his hand. The children of God, indeed, are prudent, but their prudence is altogether different from that of the flesh. Under the guidance and government of the Holy Spirit, they take every necessary precaution against snares, but in such a manner as not to practice any craftiness.

Footnotes

1 - Horsley renders the word, "Those who seek concealment." In like manner, the Chaldee paraphrases it, "They that hide themselves that they may do evil."

I have not sat with vain persons - That is, I have not been found among them; I have not made them my companions. See the notes at Psalm 1:1. The word "vain" here is in contrast with those who are sincere and true. The expression would be applied to people who are false and hollow; to those who have no sincerity or solidity of character; to those who are hypocrites and pretenders. The psalmist urges it as one evidence of his attachment to God that he had not been found among that class of persons, either as making them his companions, or as taking part with them in their counsels.
Neither will I go in with dissemblers - Neither will I walk with them; neither will I be found in their company. The word here rendered "dissemblers" means properly those who are "hidden" or "concealed;" then, those who hide their purposes or designs from others, or who conceal their real character and intentions. Thus used, the word denotes hypocrites, whose real character is "concealed" or "hidden" from the world. The psalmist says that he had not associated with such people, but that His companionship had been with the open, the frank, the sincere. On this he relied as one evidence of his piety; and this is always an evidence of true religion. See the notes at Psalm 1:1.

I have not sat with vain persons - מתי שוא methey shav, men of lies, dissemblers, backbiters, etc.
Neither will I go in with dissemblers - נעלמים naalamim, the hidden ones, the dark designers, the secret plotters and conspirators in the state.

I have not (d) sat with vain persons, neither will I go in with dissemblers.
(d) He declares that they cannot walk in simplicity before God, that delight in the company of the ungodly.

I have not sat with vain persons,.... Or "men of vanity" (t); who are full of it; who are addicted to the vanities of the world; who pursue the riches, honours, pleasures, and profits of it; which is no other than walking in a vain show: whose thoughts, words, and actions are vain; who are vainly puffed up in their fleshly mind, and walk in the vanity of it; who take the name of God in vain, and whose common discourse is foolish, frothy, light, and empty; and who are men of a vain conversation, and are rash, imprudent, and deceitful: men of bad principles may very well go by this name, who are vain and unruly talkers, and whose doctrines are doctrines of vanity, and no other than vain babbling; and also men guilty of idolatrous practices, who observe lying vanities, and worship them, and lift up their souls unto them; with such vain men, in any of these senses, the psalmist would have nothing to do; he would not keep company with them, nor have any communion, consultation, and conversation with them; it may be, he may have some respect to the men that were about Saul, to whom such a character agreed; or he may say this, and what follows, to remove a calumny cast upon him and his friends; as if they that were with him were such men as here described, and in Psalm 26:5;
neither will I go in with dissemblers: or "hidden" or "unknown" persons (u), who lie in private lurking places, to murder the innocent, or secretly take away the good names and characters of men, and it is not known who they are; or who commit sin secretly; go into secret places to do their works in the dark, and hide themselves to do evil; as the Targum, Jarchi, Kimchi, and Ben Melech, interpret it; who love darkness rather than light, because their deeds are evil; or who cover themselves with lying and flattering words, that it is not known what their real intentions be; they speak one thing, and mean another; are an assembly of treacherous men: such are all deceitful workers, who lie in wait to deceive, and walk in craftiness; and hypocrites, who have the form of religion, but are strangers to the power of it; and who are to be turned away from, and avoided; the houses, assemblies, cabals, and company of such, are to be shunned; see Genesis 49:6; or such as are "signed", or "marked"; that is, infamous persons (w).
(t) "cum hominibus vanitatis", Gejerus, Michaelis. (u) "cum occultis", Vatablus, Michaelis; "absconditis", Gejerus; so Ainsworth. (w) Vide Schultens de def. Hod. ling. Hebrews. s. 188.

As exemplified by the fruits of divine grace, presented in his life, especially in his avoiding the wicked and his purposes of cleaving to God's worship.

He still further bases his petition upon his comportment towards the men of this world; how he has always observed a certain line of conduct and continues still to keep to it. With Psalm 26:4 compare Jeremiah 15:17. מתי שׁוא (Job 11:11, cf. Psalm 31:5, where the parallel word is מרמה) are "not-real," unreal men, but in a deeper stronger sense than we are accustomed to use this word. שׁוא (= שׁוא, from שׁוא) is aridity, hollowness, worthlessness, and therefore badness (Arab. su') of disposition; the chaotic void of alienation from God; untruth white-washed over with the lie of dissimulation (Psalm 12:3), and therefore nothingness: it is the very opposite of being filled with the fulness of God and with that which is good, which is the morally real (its synonym is און, e.g., Job 22:15). נעלמים, the veiled, are those who know how to keep their worthlessness and their mischievous designs secret and to mask them by hypocrisy; post-biblical צבוּעים, dyed (cf. ἀνυπόκριτος, Luther "ungefδrbt," undyed). (את) בּוא עם, to go in with any one, is a short expression for: to go in and out with, i.e., to have intercourse with him, as in Proverbs 22:24, cf. Genesis 23:10. מרע (from רעע) is the name for one who plots that which is evil and puts it into execution. On רשׁע see Psalm 1:1.

Sat - Continued with them. I have been so far from an imitation of their wicked courses, that I have avoided their company. Vain - With false and deceitful persons. Go in - Into their company.