What does the sexton mean when he says that visiting the put will be a sermon to the narrator?

When the sexton suggests that visiting the put will be a sermon to the narrator, he implies that the experience will serve as a powerful lesson or moral reflection on life and death. By witnessing the graves and the final resting places of the deceased, the narrator may gain insights into the transient nature of life, the inevitability of mortality, and the importance of valuing one's existence. The sexton is highlighting the profound impact that such a visit can have on one's perspective and understanding of their own life and choices.