The phrase "sermons in stones" comes from Shakespeare's play, As You Like It. In this scene, the exiled Duke is talking about the good that he sees in the natural world where he must now live, away from the rituals of the court.
And this our life exempt from public haunt
Finds tongues in trees, books in the running brooks,
Sermons in stones and good in every thing.
I would not change it.
Act II, Scene 1