R. Israel Meir ha-Kohen (Kagan, Hafez Hayyim, 1838–1933), rabbi, ethical writer, and talmudist; one of the most saintly figures in modern Judaism. Of humble origin, he was taught until the age of ten by his parents and then went to Vilna where he continued his studies. He did not particularly distinguish himself as a student; nevertheless, he later towered above all his contemporaries in his qualities of religious leadership. While in a yeshivah in Vilna, the Hafez Hayyim became seriously ill as a result of the very long hours he put in every day studying. This episode had a lifelong affect on him, for he became very sensitive to his students' health, always encouraging them to eat and sleep well. His surname Poupko is hardly known, nor is he referred to by his own name, but he became universally known as Hafez Hayyim, after the title of his first work. His personality, his piety, his humility of conduct, his integrity of thought and action, together with his books, exercised a tremendous influence on religious leaders, and fascinated the masses, to whom he became the admired master and leader. Hundreds of sayings full of practical wisdom are attributed to him, and hundreds of stories both factual and legendary, all rich in morals, are reported about his life. He refused to make the rabbinate his calling, and after his marriage in Radun he subsisted on a small grocery store which his wife managed and for which he did the bookkeeping. He also did his own "bookkeeping," maintaining a daily record of his own deeds to assure himself no wrong had been perpetrated by him nor any time wasted. He spent his time either learning Torah or disseminating its knowledge among others, particularly the more simple folk, whom he always encouraged in matters of learning, observance, and faith. The Hafez Hayyim did not intend to establish a yeshivah. So many students, however, flocked to him that by 1869 his home had become known as "the Radun yeshivah" or as "the Hafez Hayyim yeshivah." Forty-five years later, the yeshivah moved to a big building of its own and R. Naphtali Trup was appointed its head. For many years it was the Hafez Hayyim's responsibility to provide for the students, a task in which he was later assisted by his three sons-in-law, leaving him more time for writing, publishing, and distributing his books. When he was 35 he published anonymously in Vilna (1873) his first book, Hafez Hayyim, devoted entirely to an exposition of the primary importance of the laws of slander, gossip, and tale bearing. Throughout his life, he laid great emphasis on the careful observance of these laws, so generally neglected in spite of the fact that their transgression involves the violation of numerous prohibitions. In 1879 he published another book on the same subject and a third in 1925. He even composed a special prayer to be recited every morning asking for protection from the sins of slander and gossip. According to a popular legend, whenever anyone would gossip in his presence, the Hafez Hayyim would fall asleep so as not to listen. His best-known and most widely studied work is his six-volume Mishnah Berurah (1894–1907), a comprehensive commentary on Shulhan Arukh, Orah Hayyim which has been accepted as an indispensable reference book on practical everyday halakhic matters. One hundred years later it is still studied and referred to widely.

שם המחבר בשולי השער, באותיות קיריליות: Kagan .M. נוסף שער-מעטפת בסדר שונה, בתוך מסגרת. ח"ד פרידברג, בית עקד ספרים, I, תל-אביב תשי"א, עמ' 190, מס' 152, רושם שם המחבר: מרדכי הכהן. נגרר אחרי שמואל ווינער, קהלת משה, עמ' 233, מס' 1894, שפענח כן את שם המחבר, שנדפס ברוסית, על-פי ההוצאה השניה שבשערה נזכר ר' מרדכי הכהן. עי' להלן . ואולם באמת נתחבר הספר על-ידי ר' ישראל מאיר הכהן, כעדות בנו ר' אריה ליב הכהן פופקא, בספרו מכתבי הרב חפץ חיים, וורשה תרצ"ז (תרצ"ט), עמ' 40. "דיני נדה" של ר' שלמה זלמן ליפשיץ נדפסו ביידיש, ווארשא [תקצ"ד], ותורגמו לעברית בידי ר' יצחק גרודזינסקי, עי' שם.