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 Psalms 109:10, will apply to this verse and the following.