Very rare incunabular printing of a sermon preached by the Abbas d'Aguilar, or Daguilar, inquisitor general of Aragon, on the occasion of the brutal execution of Juan de Esperandeu and Vidal de Urango for consipiracy in the assassination of Pedro Arbues, then inquisitor of Aragon. Esperandeu had both his hands chopped off, then was dragged with his co-conspirator to the market-pace and beheaded, after which the two were quartered and finally burned. This violence was part of the turmoil wrought by the Inquisition in Spain, as the religious institution was co-opted by the newly united government of Spain under Ferdinand and Isabella to solidify their rule and purify the religious orders. The "Conversos" (forcibly converted Muslims) and "Maranos" (converted Jews) saw their people tortured and murdered, and their lands confiscated, by their persecutors, and occasionally fought back, to be brutally suppressed. This significant sermon, indicative of the seminal changes being wrought in Spanish society, was printed on the first press in Burgos. There are no copies listed on RLIN, and a very old bookseller's catalogue entry laid in indicates it to be one of only three known copies, with the only one in America residing in the Library of the Hispanic Society of America.