There is thy gold worse poison to men's souls Doing more murders in this loathsome world Than these poor compounds that thou mayst not sell mean?

It is a dialogue in Shakespeare's Romeo and Julietbetween Romeo and the apothecary. In that scene he is buying the poison that will kill him, as he thinks Juliet is dead and no longer wishes to live.

In this statement he means that the gold he is paying the apothecary has caused more men to become murderous and caused more damage in the world than the poison that he is buying.