Augustine Thompson, Francis of Assisi: A New Biography (Ithaca: Cornell UP, 2012):
It is telling that even after years of public speaking, Francis chose to mime his last sermon to the nuns of San Damiano, not using any words. Asked to preach one last time to the sisters, Francis recited the penitential psalm, the Miserere, sat on the ground, and sprinkled ashes on his head. Doing penance made a better sermon than talking about it (p. 42).
As you may have guessed, I'm now reading Augustine Thompson's wonderful new biography of Francis of Assisi. I may be regaling you with tidbits from the book in coming days. I hope that these will be of interest to those who are now wondering about the story of the saint to whom the present pope has linked his papal ministry by choosing the name Francis.