Let the extortioner catch all that he hath - literally, "Let the extortioner cast a snare over all that he hath;" that is, let him seize all his property. The word rendered "catch" - נקשׁ nâqash - is a word which means to lay a snare, as for birds and wild animals, and hence, it means to ensnare, to entrap, to catch. The word rendered "extortioner" means literally one who lends or borrows money; a money-loaner; in our times, a "broker." Here it refers to one who loaned money on interest; or who took advantage of the necessities of others to lend money at high rates - thus sooner or later seizing upon and securing the property of another. The prayer here is, that he might be in such circumstances as to make it necessary to fall into the hands of those who would thus come into possession of all his property.
And let the strangers spoil his labor - Let strangers "plunder" his labor; that is, the fruit of his labor. Let them seize and possess what he has earned and gained to enjoy it themselves. The remarks made on Psalm 109:10, will apply to this verse and the following.

Let the strangers spoil his labor - Many of these execrations were literally fulfilled in the case of the miserable Jews, after the death of our Lord. They were not only expelled from their own country, after the destruction of Jerusalem, but they were prohibited from returning; and so taxed by the Roman government, that they were reduced to the lowest degree of poverty. Domitian expelled them from Rome; and they were obliged to take up their habitation without the gate Capena, in a wood contiguous to the city, for which they were obliged to pay a rent, and where the whole of their property was only a basket and a little hay. See Juvenal, Sat. ver. 11: -
Substitit ad veteres arcus, madidamque Capenam:
Hic ubi nocturne Numa constituebat amicae,
Nunc sacri fontis nemus, et delubra locantur
Judaes: quorum cophinus, foenumque supellex:
Omnis enim populo mercedem pendere jussa est
Arbor, et ejectis mendicat silva Camoenis.
He stopped a little at the conduit gate,
Where Numa modelled once the Roman state;
In nightly councils with his nymph retired:
Though now the sacred shades and founts are hired
By banished Jews, who their whole wealth can lay
In a small basket, on a wisp of hay.
Yet such our avarice is, that every tree
Pays for his head; nor sleep itself is free;
Nor place nor persons now are sacred held,
From their own grove the Muses are expelled.
Dryden.
The same poet refers again to this wretched state of the Jews, Sat. vi., ver. 541; and shows to what vile extremities they were reduced in order to get a morsel of bread: -
Cum dedit ille locum, cophino foenoque relicto,
Arcanam Judaea tremens mendicat in aurem,
Interpres legum Solymarum, et magna sacerdos
Arboris, ac summi fida internuncia coeli.
Implet et illa manum, sed parcius, aere minuto.
Qualia cunque voles Judaei somnia vendunt.
Here a Jewess is represented as coming from the wood mentioned above, to gain a few oboli by fortune-telling; and, trembling lest she should be discovered, she leaves her basket and hay, and whispers lowly in the ear of some female, from whom she hopes employment in her line. She is here called by the poet the interpretess of the laws of Solymae, or Jerusalem, and the priestess of a tree, because obliged, with the rest of her nation, to lodge in a wood; so that she and her countrymen might be said to seek their bread out of desolate places, the stranger having spoiled their labor. Perhaps the whole of the Psalm relates to their infidelities, rebellions, and the miseries inflicted on them from the crucifixion of our Lord till the present time. I should prefer this sense, if what is said on Psalm 109:20 be not considered a better mode of interpretation.

Let (f) the extortioner catch all that he hath; and let the strangers spoil his labour.
(f) He declares that the curse of God lies on the extortioners, who thinking to enrich their children by their unlawfully gotten goods, are by God's just judgment deprived of all.

Let the extortioner catch all that he hath,.... Or, "lay a snare for all" (c); as the Romans did, by bringing in their army, invading the land of Judea, and besieging the city of Jerusalem; who are "the extortioner or exacter that demanded tribute of them"; which they refused to pay, and therefore they seized on all they had for it. The Syriac and Arabic versions render it, "the creditor"; who sometimes for a debt would take wife and children, and all that a man had; see 2-Kings 4:1. It might be literally true of Judas; who dying in debt, his wife and children, and all he had, might be laid hold on for payment.
And let the stranger spoil his labour; plunder his house of all his goods and substance he had been labouring for: which was true of the Romans, who were aliens from the commonwealth of Israel; who came into the land, and spoiled their houses, fields, and vineyards, they had been labouring in; they took away their place and nation, and all they had, John 11:48.
(c) "illaqueet", Pagninus, Montanus, Musculus, Piscator, Gejerus; "iretiat", Vatablus, Michaelis.

The Piel נקּשׁ properly signifies to catch in snares; here, like the Arabic Arab. nqš, II, IV, corresponding to the Latin obligare (as referring to the creditor's right of claim); nosheh is the name of the creditor as he who gives time for payment, gives credit (vid., Isaiah 24:2). In Psalm 109:12 משׁך חסד, to draw out mercy, is equivalent to causing it to continue and last, Psalm 36:11, cf. Jeremiah 31:3. אחריתו, Psalm 109:13, does not signify his future, but as Psalm 109:13 (cf. Psalm 37:38) shows: his posterity. יהי להכרית is not merely exscindatur, but exscindenda sit (Ezekiel 30:16, cf. Joshua 2:6), just as in other instances חיה ל corresponds to the active fut. periphrasticum, e.g., Genesis 15:12; Isaiah 37:26. With reference to ימּח instead of ימּח (contracted from ימּחה), vid., Ges. 75, rem. 8. A Jewish acrostic interpretation of the name ישׁוּ runs: ימּח שׁמו וזכרו. This curse shall overtake the family of the υἱὸς τῆς ἀπωλείας. All the sins of his parents and ancestors shall remain indelible above before God the Judge, and here below the race, equally guilty, shall be rooted out even to its memory, i.e., to the last trace of it.

Catch - Hebrews. ensnare, take away not only by oppression but also by cunning artificers. Stranger - Who hath no right to his goods.