The lives of people are spoken of as if they are as insignificant as shadows. Alternate translation: "Everyone disappears like shadows do" (See: [[rc://en/ta/man/translate/figs-simile]])
Here it is implied that they do not know what will happen to their wealth after they die. The full meaning of this statement can be made explicit. (See: [[rc://en/ta/man/translate/figs-explicit]])