A Commentary, Critical, Practical, and Explanatory on the Old and New Testaments, by Robert Jamieson, A.R. Fausset and David Brown  at sacred-texts.com
ecc 10:1(Ecc. 10:1-20)
Following up Ecc 9:18.
him that is in reputation--for example, David (Sa2 12:14); Solomon (1Ki. 11:1-43); Jehoshaphat (2Ch. 18:1-34; Ch2 19:2); Josiah (Ch2 35:22). The more delicate the perfume, the more easily spoiled is the ointment. Common oil is not so liable to injury. So the higher a man's religious character is, the more hurt is caused by a sinful folly in him. Bad savor is endurable in oil, but not in what professes to be, and is compounded by the perfumer ("apothecary") for, fragrance. "Flies" answer to "a little folly" (sin), appropriately, being small (Co1 5:6); also, "Beelzebub" means prince of flies. "Ointment" answers to "reputation" (Ecc 7:1; Gen 34:30). The verbs are singular, the noun plural, implying that each of the flies causes the stinking savor.
ecc 10:2(Ecc 2:14).
right--The right hand is more expert than the left. The godly wise is more on his guard than the foolish sinner, though at times he slip. Better a diamond with a flaw, than a pebble without one.
ecc 10:3by the way--in his ordinary course; in his simplest acts (Pro 6:12-14). That he "saith," virtually, "that he" himself, &c. [Septuagint]. But Vulgate, "He thinks that every one (else whom he meets) is a fool."
yielding pacifieth-- (Pro 15:1). This explains "leave not thy place"; do not in a resisting spirit withdraw from thy post of duty (Ecc 8:3).
ecc 10:5as--rather, "by reason of an error" [MAURER and HOLDEN].
ecc 10:6rich--not in mere wealth, but in wisdom, as the antithesis to "folly" (for "foolish men") shows. So Hebrew, rich, equivalent to "liberal," in a good sense (Isa 32:5). Mordecai and Haman (Est 3:1-2; Est 6:6-11).
ecc 10:7servants upon horses--the worthless exalted to dignity (Jer 17:25); and vice versa (Sa2 15:30).
ecc 10:8The fatal results to kings of such an unwise policy; the wrong done to others recoils on themselves (Ecc 8:9); they fall into the pit which they dug for others (Est 7:10; Psa 7:15; Pro 26:27). Breaking through the wise fences of their throne, they suffer unexpectedly themselves; as when one is stung by a serpent lurking in the stones of his neighbor's garden wall (Psa 80:12), which he maliciously pulls down (Amo 5:19).
ecc 10:9removeth stones--namely, of an ancient building [WEISS]. His neighbor's landmarks [HOLDEN]. Cuts out from the quarry [MAURER].
endangered--by the splinters, or by the head of the hatchet, flying back on himself. Pithy aphorisms are common in the East. The sense is: Violations of true wisdom recoil on the perpetrators.
ecc 10:10iron . . . blunt--in "cleaving wood" (Ecc 10:9), answering to the "fool set in dignity" (Ecc 10:6), who wants sharpness. More force has then to be used in both cases; but "force" without judgment "endangers" one's self. Translate, "If one hath blunted his iron" [MAURER]. The preference of rash to judicious counsellors, which entailed the pushing of matters by force, proved to be the "hurt" of Rehoboam (1Ki. 12:1-33).
wisdom is profitable to direct--to a prosperous issue. Instead of forcing matters by main "strength" to one's own hurt (Ecc 9:16, Ecc 9:18).
ecc 10:11A "serpent will bite" if "enchantment" is not used; "and a babbling calumniator is no better." Therefore, as one may escape a serpent by charms (Psa 58:4-5), so one may escape the sting of a calumniator by discretion (Ecc 10:12), [HOLDEN]. Thus, "without enchantment" answers to "not whet the edge" (Ecc 10:10), both expressing, figuratively, want of judgment. MAURER translates, "There is no gain to the enchanter" (Margin, "master of the tongue") from his enchantments, because the serpent bites before he can use them; hence the need of continual caution. Ecc 10:8-10, caution in acting; Ecc 10:11 and following verses, caution in speaking.
ecc 10:12gracious--Thereby he takes precaution against sudden injury (Ecc 10:11).
swallow up himself-- (Pro 10:8, Pro 10:14, Pro 10:21, Pro 10:32; Pro 12:13; Pro 15:2; Pro 22:11).
ecc 10:13Illustrating the folly and injuriousness of the fool's words; last clause of Ecc 10:12.
ecc 10:14full of words-- (Ecc 5:2).
a man cannot tell what shall be-- (Ecc 3:22; Ecc 6:12; Ecc 8:7; Ecc 11:2; Pro 27:1). If man, universally (including the wise man), cannot foresee the future, much less can the fool; his "many words" are therefore futile.
ecc 10:15labour . . . wearieth-- (Isa 55:2; Hab 2:13).
knoweth not how to go to the city--proverb for ignorance of the most ordinary matters (Ecc 10:3); spiritually, the heavenly city (Psa 107:7; Mat 7:13-14). MAURER connects Ecc 10:15 with the following verses. The labor (vexation) caused by the foolish (injurious princes, Ecc 10:4-7) harasses him who "knows not how to go to the city," to ingratiate himself with them there. English Version is simpler.
ecc 10:16a child--given to pleasures; behaves with childish levity. Not in years; for a nation may be happy under a young prince, as Josiah.
eat in the morning--the usual time for dispensing justice in the East (Jer 21:12); here, given to feasting (Isa 5:11; Act 2:15).
ecc 10:17son of nobles--not merely in blood, but in virtue, the true nobility (Sol 7:1; Isa 32:5, Isa 32:8).
in due season-- (Ecc 3:1), not until duty has first been attended to.
for strength--to refresh the body, not for revelry (included in "drunkenness").
ecc 10:18building--literally, "the joining of the rafters," namely, the kingdom (Ecc 10:16; Isa 3:6; Amo 9:11).
hands-- (Ecc 4:5; Pro 6:10).
droppeth--By neglecting to repair the roof in time, the rain gets through.
ecc 10:19Referring to Ecc 10:18. Instead of repairing the breaches in the commonwealth (equivalent to "building"), the princes "make a feast for laughter (Ecc 10:16), and wine maketh their life glad (Psa 104:15), and (but) money supplieth (answereth their wishes by supplying) all things," that is, they take bribes to support their extravagance; and hence arise the wrongs that are perpetrated (Ecc 10:5-6; Ecc 3:16; Isa 1:23; Isa 5:23). MAURER takes "all things" of the wrongs to which princes are instigated by "money"; for example, the heavy taxes, which were the occasion of Rehoboam losing ten tribes (Kg1 12:4, &c.).
ecc 10:20thought--literally, "consciousness."
rich--the great. The language, as applied to earthly princes knowing the "thought," is figurative. But it literally holds good of the King of kings (Psa. 139:1-24), whose consciousness of every evil thought we should ever realize.
bed-chamber--the most secret place (Kg2 6:12).
bird of the air, &c.--proverbial (compare Hab 2:11; Luk 19:40); in a way as marvellous and rapid, as if birds or some winged messenger carried to the king information of the curse so uttered. In the East superhuman sagacity was attributed to birds (see on Job 28:21; hence the proverb).