The sense is: "The fool wearies himself with ineffectual attempts, he has not sufficient knowledge for the transaction of ordinary business."

He knoweth not how to go to the city - I suppose this to be a proverb: "He knows nothing; he does not know his way to the next village." He may labor; but for want of judgment he wearies himself to no purpose.

The labour of the foolish wearieth every one of them, because he knoweth not how to go to the (g) city.
(g) The ignorance and beastliness of the wicked is such that they know not common things, and yet will discuss high matters.

The labour of the foolish wearieth everyone of them,.... The labour of fools, both in speaking and doing, weary those who have any concern with them, and themselves likewise, since all their labour is vain and fruitless;
because he knoweth not how to go to the city; to any city, the road to which is usually broad, and plain and easy to be found, and yet cannot be found by the foolish man; showing, that he that talks of abstruse things, things too high and wonderful for him, which he affects to know, must needs be a stranger to them, since things the most easy to be understood he is ignorant of, and wearies himself to find; or he does not know how to behave himself in a city, among citizens, in a civil and polite manner. The Targum is,
"he learns not to go to the city, where wise men dwell, to learn instruction from it.''
Some interpret it of the city of Jerusalem, where were the temple, sanhedrim, synagogues, schools, &c. but it may be better applied to the heavenly city, the New Jerusalem, which fools or wicked men know not the way unto, nor do they seek after it; see Psalm 107:7; so Alshech interprets it of heaven.

labour . . . wearieth-- (Isaiah 55:2; Habakkuk 2:13).
knoweth not how to go to the city--proverb for ignorance of the most ordinary matters (Ecclesiastes 10:3); spiritually, the heavenly city (Psalm 107:7; Matthew 7:13-14). MAURER connects Ecclesiastes 10:15 with the following verses. The labor (vexation) caused by the foolish (injurious princes, Ecclesiastes 10:4-7) harasses him who "knows not how to go to the city," to ingratiate himself with them there. English Version is simpler.

"The labour of the foolish wearieth him who knoweth not how to go to the city." If we do not seek to explain: labour such as fools have wearies him (the fool), then we have here such a synallage numeri as at Isaiah 2:8; Hosea 4:8, for from the plur. a transition is made to the distributive or individualizing sing. A greater anomaly is the treatment of the noun עמל as fem. (greater even than the same of the noun pithgam, Ecclesiastes 8:11, which admitted of attractional explanation, and, besides, in a foreign word was not strange). Kimchi, Michlol 10a, supposes that עמל is thought of in the sense of עמל יגיעת; impossible, for one does not use such an expression. Hitzig, and with him Hengst., sees the occasion for the synallage in the discordance of the masc. ייגּענּוּ; but without hesitation we use the expressions ייחל, Micah 5:6, ייסּ, Joshua 6:26, and the like. 'Amal also cannot be here fem. unitatis (Bttch. 657. 4), for it denotes the wearisome striving of fools as a whole and individually. We have thus to suppose that the author has taken the liberty of using 'amal once as fem. (vid., on the contrary, Ecclesiastes 2:18, Ecclesiastes 2:20), as the poet, Proverbs 4:13, in the introduction of the Book of Proverbs uses musar once as fem., and as the similarly formed צבא is used in two genders. The fool kindles himself up and perplexes himself, as if he could enlighten the world and make it happy, - he who does not even know how to go to the city. Ewald remarks: "Apparently proverbial, viz., to bribe the great lords in the city." For us who, notwithstanding Ecclesiastes 10:16, do not trouble ourselves any more with the tyrants of Ecclesiastes 10:4, such thoughts, which do violence to the connection, are unnecessary. Hitzig also, and with him Elst. and Zckl., thinks of the city as the residence of the rulers from whom oppression proceeds, but from whom also help against oppression is to be sought. All this is to be rejected. Not to know how to go to the city, is = not to be able to find the open public street, and, like the Syrians, 2-Kings 6:18., to be smitten with blindness. The way to the city is via notissima et tritissima. Rightly Grotius, like Aben Ezra: Multi quaestionibus arduis se faitgant, cum ne obvia quidem norint, quale est iter ad urbem. אל־עיר is vulgar for אל־העיר. In the Greek language also the word πόλις has a definite signification, and Athens is called ἄστυ, mostly without the art. But Stamboul, the name of which may seem as an illustration of the proverbial phrase, "not to know how to go to the city," is = εἰς τὴν πόλιν. Grtz finds here an allusion to the Essenes, who avoided the city - habeat sibi!

Wearieth - Fools discover their folly by their wearisome and fruitless endeavours after things which are too high for them. Because - He is ignorant of those things which are most easy, as of the way to the great city whither he is going.