This is another of Solomon’s “He who…” statements found fairly abundantly throughout the Book. They go pretty much just like the one in this verse. Whoever ______________ is doing ____________ to God. In this case both sides of the equation are clearly negative and wholly undesirable, not to mention absolutely unBiblical for a believer. Often, the essence of the statement is most often one that makes complete and obvious sense as well. It also seems that the action of mocking is one of Solomon’s particular dislikes. And, of course, anything that either dishonors or brings reproach upon His reputation among men likewise earns Solomon’s active disdain.
“Whoso”, as it is translated in some version is the older English way of simply saying “The one who…” (as it might actually say in your version). It points to the perpetrator of the act in view as well as providing the implication that we are not talking about a single target, but rather, a generalized statement that applies to absolutely everyone who performs the act under scrutiny. In this case it is English word “mock”. Everyone, in general, who “mocks the poor” is actually and actively doing what Solomon refers to in a moment. Mock is not a very widely used word in the OT. It comes from a 15th century French word, “marquee” meaning to “treat with contempt or ridicule”. It can also mean “to disappoint the hopes on the one (or ones) in view; here…the poor. It is only used 18 times in the OT, rendered mock 8 times, scorn 3x, laugh at 3x, to “hold in derision 2x, as well as a couple other forms depending on the particular translation in mind. Inherent in the word is the idea of scorn or derision in the mind that prompts the action.
The stated object of this “mocking” (or other uses) is said to be “the poor”. Poor, of course, refers to the one who has little or no wealth. It can also refer to the condition of lack, not speaking of monetary lack, but the lacking of whatever objective situation is in perspective. One can be “poor” in influence, for instance. It is also interesting that this “poor” quality can be something that is the result of ones’ own actions (or lack of action). The poor quality or neediness is just as valid, but the cause is different.
It is not the condition of poorness or poverty that Solomon is mainly commenting on in this verse. Rather, it is the matter of “mocking” those who are in that condition. As Wes noted, Solomon, by using this term in speaking of how Someone speaks of or treats those “poor” that he is drawing our attention toward. It has to do, not so much with the idea of walking around verbally make fun of them; butt rather of the inner attitude that one holds toward them.