Paul says basically the same thing twice for emphasis. AT: "he would realize that he is guilty of sin because he hears what you are saying" (See: [[rc://en/ta/man/translate/figs-parallelism]])
Here "heart" is a metonym for a person's thoughts. This can be stated in active form. AT: "God would reveal to him the secrets of his heart" or "He would recognize his own private inner thoughts" (See: [[rc://en/ta/man/translate/figs-metonymy]] and [[rc://en/ta/man/translate/figs-activepassive]])