The Yosif Omez is a valuable source book for the history of the contemporary Frankfort Jewish community. Hahn mentions, for instance, the local Purim (Adar 20), instituted to commemorate the hanging of Fettmilch (no. 1107–09). He also records the comparatively slight damage suffered by the community as a result of the passage of soldiers through the area during the Thirty Years' War. The Yosif Omez is written in a pious vein, and the concluding chapters are devoted to ethics. In the sections on pedagogy, Hahn deplored the ignorance of the Bible prevalent among rabbis of his day. He suggested that a boy who showed no sign of progress in the study of the Talmud by the age of 13 be withdrawn from its study and taught Bible instead.

R. Joseph Yuspa b. Phinehas Seligmann Hahn (Nordlingen) (1570–1637), German rabbi and author. Hahn spent all his life in Frankfort. He was present during the Fettmilch riots, the subsequent expulsion of the Jews from the city in 1614, and their triumphant return two years later after Fettmilch was hanged. Hahn was head of the Frankfort bet din and of the local yeshivah. When there was no other incumbent, he also filled the office of communal rabbi. Hahn was a contemporary and colleague of R. Isaiah Horowitz (Shelah). In 1718, Joseph Kosman, one of Hahn's descendants, published his own Noheg Ka-Zon Yosef in Hanau, in which he quoted freely from his kinsman's work, sometimes without indicating his source.

דף [6, ב-7]: "הקדמה מהדיין חתנו של מחבר", ר' משה רייש דארום. יש הבדלים ניכרים בין כתבי היד של החיבור ואף בין הטפסים של הספר המודפס. השינויים בין הטפסים הנדפסים הם בסעיפים תפד-תצג: בעת ההדפסה נשמטו כמה סעיפים שיש בהם משום תרעומת הגויים. עיין: ש. אש, שינויים ב"יוסף אומץ" והרקע ההיסטורי, קובץ לזכרו של אליעזר שמיר, שדה-אליהו תשי"ח, עמ' 162-155.