Adam Clarke on Proverbs 13:7

There is that maketh himself rich - That labors hard to acquire money, yet hath nothing; his excessive covetousness not being satisfied with what he possesses, nor permitting him to enjoy with comfort what he has acquired. The fable of the dog in the manger will illustrate this.

There is that maketh himself poor, yet hath great riches - "As poor," said St. Paul, "yet making many rich; as having nothing, yet possessing all things." The former is the rich poor man; the latter is the poor rich man.

As the words are here in the hithpael conjugation, which implies reflex action, or the action performed on one's self, and often signifies feigning or pretending to be what one is not, or not to be what one is; the words may be understood of persons who feign or pretend to be either richer or poorer than they really are, to accomplish some particular purpose. "There is that feigneth himself to be rich, yet hath nothing; there is that feigneth himself to be poor, yet hath great riches." Both these characters frequently occur in life.