Destroy thyself - The Septuagint and Vulgate render it: "be amazed." Compare "marvel not" Ecclesiastes 5:8.

Why shouldest thou destroy thyself? - תשומם tishshomem, make thyself desolate, so that thou shalt be obliged to stand alone; neither make thyself over-wise, תתחכם tithchaccam, do not pretend to abundance of wisdom. Why shouldest thou be so singular? In other words, and in modern language, "There is no need of all this watching, fasting, praying, self-denial, etc., you carry things to extremes. Why should you wish to be reputed singular and precise?" To this the man of God answers:

Be not righteous (m) over much; neither make thyself over wise: why shouldest thou destroy thyself?
(m) Do not boast too much of your own justice and wisdom.

Be not righteous over much,.... This is not meant of true and real righteousness, even moral righteousness, a man cannot be too holy or too righteous; but of a show and ostentation of righteousness, and of such who would be thought to be more righteous and holy than others, and therefore despise those who, as they imagine, do not come up to them; and are very rigid and censorious in their judgment of others, and very severe in their reproofs of them; and, that they may appear very righteous persons, will do more than what the law requires of them to do, even works of supererogation, as the Pharisees formerly, and Papists now, pretend, and abstain from the lawful use of things which God has given to be enjoyed; and macerate their bodies by abstinence, fastings, pilgrimages, penance, scourges, and the like, as the Eremites among the Christians, and the Turks, as Aben Ezra on the place observes; and many there be, who, by an imprudent zeal for what they judge right, and which sometimes are mere trifles, and by unseasonable reproofs for what is wrong, expose themselves to resentment and danger. Some understand this of political and punitive justice, exercising it in too strict and rigorous a manner, according to the maxim, "summum jus saepe summa injuria est" (w); and Schultens (x), from the use of the word in the Arabic language, renders it, "be not too rigid"; and others, in a contrary sense, of too much mercy and pity to offenders. So the Midrash; and Jarchi illustrates it by the case of Saul, who had mercy on the wicked, and spared Agag. The Targum is,
"be not over righteous at a time that a sinner is found guilty of slaughter in thy court of judicature, that thou shouldest spare and not kill him;''
neither make thyself over wise; above what is written, or pretend to be wiser than others. So the Arabic version, "show not too much wisdom"; do not affect, as not to be more righteous than others, so not more wise, by finding fault with present times, or with the dispensations of Providence, or with the manners and conduct of men; setting up for a critic and a censurer of men and things; or do not pry into things, and seek after a knowledge of them, which are out of your reach, and beyond your capacity;
why shouldest thou destroy thyself? either by living too strictly and abstemiously, or by studying too closely, or by behaving in such a manner to men, as that they will seek thy destruction, and bring it on thee: or "why shouldest thou", or "whereby", or "lest, thou shouldest be stupid" (y); lose thy sense and reason, as persons who study the knowledge of things they have not a capacity for: or why shouldest thou become foolish in the eyes of all men by thy conduct and behaviour? or, "why shouldest thou be desolate" (z); alone, and nobody care to have any conversation and acquaintance with thee?
(w) Terent. Heautont. Acts. 4. Sc. 4. (x) De Defect. Hod. Ling. Hebrews. s. 230. (y) "ut quid obstupesces?" Vatablus, Amama; "cur obstupesces?" Mercerus; "cur in stuporem te dares?" Cocceius; "qua teipsum stupidum facies?" Tigurine version; "ne obstupescas", V. L. so Sept. and Syriac versions. (z) "Ne quid desolaberis?" Pagninus, Montanus; "quare desolationem tibi accerseres?" Junius & Tremellius, Piscator, Gejerus.

HOLDEN makes Ecclesiastes 7:16 the scoffing inference of the objector, and Ecclesiastes 7:17 the answer of Solomon, now repentant. So (1-Corinthians 15:32) the skeptic's objection; (1-Corinthians 15:33) the answer. However, "Be not righteous over much," may be taken as Solomon's words, forbidding a self-made righteousness of outward performances, which would wrest salvation from God, instead of receiving it as the gift of His grace. It is a fanatical, pharisaical righteousness, separated from God; for the "fear of God" is in antithesis to it (Ecclesiastes 7:18; Ecclesiastes 5:3, Ecclesiastes 5:7; Matthew 6:1-7; Matthew 9:14; Matthew 23:23-24; Romans 10:3; 1-Timothy 4:3).
over wise-- (Job 11:12; Romans 12:3, Romans 12:16), presumptuously self-sufficient, as if acquainted with the whole of divine truth.
destroy thyself--expose thyself to needless persecution, austerities and the wrath of God; hence to an untimely death. "Destroy thyself" answers to "perisheth" (Ecclesiastes 7:15); "righteous over much," to "a just man." Therefore in Ecclesiastes 7:15 it is self-justiciary, not a truly righteous man, that is meant.

Be not - This verse and the next have a manifest reference to Ecclesiastes 7:15, being two inferences drawn from the two clauses of the observation. Solomon here speaks in the person of an ungodly man, who takes occasion to dissuade men from righteousness, because of the danger which attends it. Therefore, saith he, take heed of strictness, zeal, and forwardness in religion. And the next verse contains an antidote to this suggestion; yea, rather saith he, be not wicked or foolish overmuch; for that will not preserve thee, as thou mayest imagine, but will occasion and hasten thy ruin.