This article provides a re-examination of several crucial aspects of Agnolo Bronzino's Holy Family in Vienna. The painting, mentioned by Vasari and executed for Bartolomeo Panciatichi c. 1545 — early 1550s, was meticulously revised and altered several times by Bronzino, as is revealed by the recent examination with infrared-reflectography and restoration of the painting. An important detail in the painting is a Hebrew word painted on the book supported by the Virgin. While earlier scholars had identified this word "Jesus", this article suggests that instead it is "Isaiah", which would be more suitable to a Holy Family because one of the Prophet Isaiah's most famous prophecies was that of the Birth of Christ. It is proposed that the sources for the Hebrew lettering and phonetic spelling of the word "Isaiah" are to be found in the texts being studied by members of the Florentine literary academy, the Accademia Fiorentina, and in particular those referred to by Pierfrancesco Giambullari in his Il Gello di M. Pierfrancesco Giambullari Accademico Fiorentino, Florence, 1546, such as the works of Sebastian Münster and Sante Pagnino. The patron of the picture, Bartolomeo Panciatichi, who was suspected of unorthodox faith, persecuted for having Lutheran books in 1552, and who was also a member of the Accademia Fiorentina, may have seen the inclusion of the book of "Isaiah" as a veiled reference to traditions more fundamental than those of the modern Catholic church. He would also have been in a position to appreciate the fact that in "Isaiah" in Hebrew means "the Salvation of the Lord", which could allude to the doctrine of salvation through Christ alone.