Hath much sorrow - Rather, is very sad and hath pain and vexation.

All his days also he eateth in darkness - Even his enjoyments are embittered by uncertainty. He fears for his goods; the possibility of being deprived of them fills his heart with anguish. But instead of יאכל yochel, "he shall eat," ילך yelech, "he shall walk," is the reading of several MSS. He walks in darkness - he has no evidence of salvation. There is no ray of light from God to penetrate the gloom; and all beyond life is darkness impenetrable!
And wrath with his sickness - His last hours are awful; for,
"Counting on long years of pleasure here,
He's quite unfurnish'd for the world to come."
Blair.
He is full of anguish at the thought of death; but the fear of it is horrible. But if he have a sense of God's wrath in his guilty conscience, what horror can be compared with his horror!

All his days also he eateth in (n) darkness, and [he hath] much sorrow and wrath with his sickness.
(n) In affliction and grief of mind.

All his days also he eateth in darkness,.... To all that has been said is added another evil, that attends such whose hearts are inordinately set on riches; that all their days, throughout the whole of their lives, they live a most uncomfortable life; for eating is here put for their whole manner of living: such not only eat coarse bread, and very mean food of any sort, but wear sordid apparel, and live in a poor cottage, in a very obscure and miserable manner. Aben Ezra understands it literally of the night, to which time such a man defers eating, that he might lose no time in his labour; and that it might not be seen what sort of food he eats, and how sparingly, and that others might not eat with him; and what he does eat is not eaten freely, but grudgingly, and with anguish and distress of mind, without any real pleasure and joy; and much less with the light of God's countenance, the discoveries of his love, and communion with him: the Targum is,
"all his days he dwelleth in darkness, that he may taste his bread alone;''
and he hath, much sorrow and wrath with his sickness; either the sickness of his mind, his covetousness; or the sickness of his body, emaciated by withholding from himself the necessaries of life: or when he comes upon a sick bed, he is filled with sorrow and indignation, that he must live no longer, to accumulate more wealth, and accomplish his projects and designs; and that he must leave his wealth, he has been at so much pains to gather together. Or, "and he is much angry" (o); when things do not answer in trade according to his wishes; when his substance diminishes, or, however, does not increase as he desires; when he is cheated by fraudulent men, or robbed by thieves: "and he hath sickness" (p); either of body or mind, or both, because matters do not succeed as he would have them; and through fretfulness at losses and crosses, and disappointments; and through cares in getting and keeping what he has: "and wrath"; at all about him, whom he is ready to charge with slothfulness or unfaithfulness to him; and even at the providence of God, that does not give him the desired success; so that he has no manner of pleasure and comfort in life.
(o) "et irascitur multum", Vatablus, Drusius; "et indignatus fuit, vel indignatur multum", Piscator, Rambachius. (p) "et agritudo ei fuit, vel est", Piscator, Drusius; "vel fuerit", Gejerus.

eateth--appropriately put for "liveth" in general, as connected with Ecclesiastes 5:11-12, Ecclesiastes 5:18.
darkness--opposed to "light (joy) of countenance" (Ecclesiastes 8:1; Proverbs 16:15).
wrath--fretfulness, literally, "His sorrow is much, and his infirmity (of body) and wrath."

"Also all his life long he eateth in darkness and grieveth himself much, and oh for his sorrow and hatred!" We might place Ecclesiastes 5:16 under the regimen of the שׁ of שׁיע of Ecclesiastes 5:15; but the Hebrews. style prefers the self-dependent form of sentences to that which is governed. The expression Ecclesiastes 5:16 has something strange. This strangeness disappears if, with Ewald and Heiligst., after the lxx and Jerome, for יאכל we read ואכל: καὶ ἐν πένθει; Bttch. prefers ואפל, "and in darkness." Or also, if we read ילך for יאכל; thus the Midrash here, and several codd. by Kennicott; but the Targ., Syr., and Masora read יאכל. Hitzig gets rid of that which is strange in this passage by taking כּל־ימיו as accus. of the obj., not of the time: all his days, his whole life he consumes in darkness; but in Hebrews. as in Lat. we say: consumere dies vitae, Job 21:13; Job 36:11, but not comedere; and why should the expression, "to eat in darkness," not be a figurative expression for a faithless, gloomy life, as elsewhere "to sit in darkness" (Micah 7:8), and "to walk in darkness"? It is meant that all his life long he ate אונים לחם, the bread of sorrow, or לחץ לחם, prison fare; he did not allow himself pleasant table comforts in a room comfortably or splendidly lighted, for it is unnecessary to understand חשׁך subjectively and figuratively (Hitz., Zck.).
In 16b the traditional punctuation is וכעס.
(Note: Thus in correct texts, in H. with the note: כ מלרע, viz., here and at Psalm 112:10, only there ע has, according to tradition, the Kametz. Cf. Mas. fin. 52b, and Baer's Ed. of Psalter, under Psalm 112:10.)
The perf. ruled by the preceding fut. is syntactically correct, and the verb כּעס is common with the author, Ecclesiastes 7:9. Hitzig regards the text as corrupt, and reads כּחליו and כּעס, and explains: and (he consumes or swallows) much grief in his, etc.; the phrase, "to eat sorrow," may be allowed (cf. Proverbs 26:6, cf. Job 15:16); but יאכל, as the representative of two so bold and essentially different metaphors, would be in point of style in bad taste. If the text is corrupt, it may be more easily rectified by reading וק לו וחלי הרבה וכּעס: and grief in abundance, and sorrow has he, and wrath. We merely suggest this. Ewald, Burger, and Bttch. read only וכעס הרבה וחלי; but לו is not to be dispensed with, and can easily be reduced to a mere vav. Elster retains וכעס, and reads, like Hitzig, בחליו: he grieves himself much in his sorrow and wrath; but in that case the word וקצפו was to be expected; also in this way the ideas do not psychologically accord with each other. However the text is taken, we must interpret וחליו וקצף as an exclamation, like הף, Isaiah 29:16; תּף, Jeremiah 49:16; Ewald, 328a, as we have done above. That וח of itself is a subst. clause = וחלי לו is untenable; the rendering of the noun as forming a clause, spoken of under Ecclesiastes 2:21, is of a different character.
(Note: Rashi regards וחליו as a form like חיתו. This o everywhere appears only in a gen. connection.)
He who by his labour and care aims at becoming rich, will not only lay upon himself unnecessary privations, but also have many sorrows; for many of his plans fail, and the greater success of others awakens his envy, and neither he himself nor others satisfy him; he is morbidly disposed, and as he is diseased in mind, so also in body, and his constantly increasing dissatisfaction becomes at last קצף, he grumbles at himself, at God, and all the world. From observing such persons, Paul says of them (1-Timothy 6:6.): "They have pierced themselves through (transfoderunt) with many sorrows."
In view of these great evils, with which the possession of riches also is connected: of their deceitful instability, and their merely belonging to this present life, Koheleth returns to his ceterum censeo.

He eateth - He hath no comfort in his estate, but even when he eats, he doth it with anxiety and discontent. And wrath - When he falls sick, and presages his death, he is filled with rage, because he is cut off before he hath accomplished his designs, and because he must leave that wealth and world in which all his hopes and happiness lie.