Unjust gain - Omit "unjust:" "usury and gain" make up the notion of "gain derived from usury." Ill-gotten gains do not prosper, after a time they pass into hands that know how to use them better.

He that by usury - increaseth his substance - By taking unlawful interest for his money; lending to a man in great distress, money, for the use of which he requires an exorbitant sum. O that the names of all those unfeeling, hard-hearted, consummate villains in the nation, who thus take advantage of their neighbour's necessities to enrich themselves, were published at every market cross; and then the delinquents all sent to their brother savages in New Zealand. It would be a happy riddance to the country.

He that by interest and unjust gain increaseth his substance, he shall gather (c) it for him that will pity the poor.
(c) For God will take away the wicked usurer, and give his goods to him that will bestow them well.

He that by usury and unjust gain increaseth his substance,.... By biting and oppressing the poor; letting him have money at an exorbitant interest, and goods at an exorbitant price, and so increases his substance in this scandalous manner; hence usury is in Leviticus 25:36, called "increase", and by the Greeks a "birth", because money is the birth of money, as Aristotle (e) observes; and so by the Latins "foenus", as if it was "foetus" (f), "a birth". The word for usury here signifies biting; and so usury, with classical writers (g), is said to bite; and while it increases the substance of the usurer, it lessens and devours that of others;
he shall gather it for him that will pity the poor; not for himself, nor for his posterity; but for such, though not intentionally but eventually, as will make a good use of it, and distribute it to the necessities of the poor. The meaning is, that things should be so overruled by the providence of God, that what such an avaricious man gets in his dishonest way should not be enjoyed by him or his; but should be taken out of his hands, and put into the hands of another, that will do good with it, by showing mercy to the poor; see Job 27:16.
(e) Politic. l. 1. c. 10. (f) A. Gell. Noct. Attic. l. 16. c. 12. (g) Plauti Pseudolos, Acts. 4. Sc. 7. v. 23, 24. "Habet argentum jam admordere hune mihi lubet", Lucan. l. 1. v. 131. "Vorax usura."

That which is ill got, though it may increase much, will not last long. Thus the poor are repaid, and God is glorified.

usury . . . unjust gain--(Compare Margin). The two terms, meaning nearly the same, may denote excessive interest. God's providence directs the proper use of wealth.

This verse continues a series of proverbs (commencing in Proverbs 28:7) beginning with a participle:
He who increaseth his wealth by interest and usury,
Gathereth it for one who is benevolent toward the lowly.
Wealth increased by covetous plundering of a neighbour does not remain with him who has scraped it together in so relentless a manner, and without considering his own advantage; but it goes finally into the possession of one who is merciful towards the poor, and thus it is bestowed in a manner that is pleasing to God (cf. Proverbs 13:22; Job 22:16.). The Kerı̂, which drops the second ב, appears to wish to mitigate the sharpness of the distinction of the second idea supposed in its repetition. But Leviticus 25:35-37, where an Israelite is forbidden to take usury and interest from his brother, the two are distinguished; and Fleischer rightly remarks that there נשׁך means usury or interest taken in money, and תרבית usury or interest taken in kind; i.e., of that which one has received in loan, such as grain, or oil, etc., he gives back more than he has received. In other words: נשׁך is the name of the interest for the capital that is lent, and מרבּית, or, as it is here called תרבית, the more, the addition thereto, the increase (Luther: ubersatz). This meaning of gain by means of lending on interest remains in נשׁך; but תרבית, according to the later usus loq., signifies gain by means of commerce, thus business-profit, vid., Baba Meza, v. 1. Instead of יקבּצנּוּ, more recent texts have the Kal
(Note: If, as Hitzig, after J. H. Michaelis, remarks, the word were Ben-Asher's יקבּצנּוּ, then it would be thus rightly punctuated by Clodius and the moderns. Kimchi, in the Wrterbuch under קבץ, adduces this word as Ben-Asher's. But the Masora knows nothing of it. It marks יקבּצנּוּ, Jeremiah 31:10, with לית as unicum, and thus supposes for the passages before us יקבּצנּוּ, which certainly is found in MSS, and is also marked on the margin with לית as unicum.)
יקבּצנּוּ. לחונן also is, as Proverbs 14:31; Proverbs 19:17, part. Kal, not inf. Poel: ad largiendum pauperibus (Merc., Ewald, Bertheau), for there the person of him who presents the gift is undefined; but just this, that it is another and better-disposed, for whom, without having it in view, the collector gathers his stores, is the very point of the thought.