Fray Bernardino de Sahagún was a Franciscan missionary who arrived in Mexico from Spain in 1529 and stayed until his death in 1590. He worked with the indigenous peoples of the area to document their cultures and religions, in large part motivated by the conviction that better understanding of their beliefs and practices would improve the efforts to convert them to Christianity. His methods have led some scholars to consider him the first ethnohistorian, and he is remembered today as much for his ethnographic and linguistic documentation of the Nahua peoples and Aztec civilization as for his missionary work. This manuscript is a key primary source for understanding Sahagún's interpretation of Christianity for his Nahua audience. It contains a bilingual text of the "Addiciones," additions written by Sahagún to supplement the “Postilla,” or scriptural commentaries, used in missionary work among the Aztecs and Nahua. The additions explain the three Christian virtues of faith, hope, and charity, with charity receiving the longest treatment. The final three chapters describe the punishments of hell; the rewards of virtue in the glories of heaven; and death and the Day of Judgment. There is also a fragment of text containing tenonotzaliztli (moral and doctrinal admonitions) condemning native rituals. An appendix copied by one of Sahagún’s scribes, Alonso Vegerano, also condemns Indian religious beliefs, with special emphasis on the role of the devil in Indian life.