יצחק אייזיק מטירנא

Rav Yitzchak Eizik of Tirna (niftar around 5185/1425), known in English sources as Isaac Tyrnau, was one of the gedolei Ashkenaz of the later Rishonim and the author of the Sefer HaMinhagim, the sefer that shaped the minhag of eastern Ashkenaz for all the generations that followed. Little is known of his life beyond his father’s name, Binyamin. He grew up in Vienna, where he learned together with the Maharil under Rav Shalom of Neustadt; his rebbe muvhak was Rav Avraham Klausner, and he learned as well under Rav Aharon Blumlein. An exchange between him and the Maharil concerning a get in 5180/1420 has been preserved. Some hold he served as rav in Vienna, in Pressburg, and in Tirna; after the gezeirot of 5181/1421 in Austria he is found in Nuremberg, and beyond that nothing more is known of his path.

After those gezeirot he composed the Sefer HaMinhagim: a summary of the minhagim of the kehillot of Austria, Hungary, and Bohemia as he had received them from his rebbeim, opening with motzaei Shabbat, weekday, Shabbat, and Rosh Chodesh, and then running through the year by the order of the months from Nisan. The Black Death of a lifetime before had all but destroyed the kehillot of Germany, and those who truly knew the local minhagim had dwindled in some places to two or three men; his stated aim was to set down what to do in practice, in language plain for every Jew — a guide for whoever comes through the doors of the beit knesset. It is the first sefer to treat the yahrzeit in detail, and appended to it is a treatise on mussar, Orchot Chayim.

First printed in Venice in 5326/1566, the Sefer HaMinhagim has since been printed more than a hundred times, with many Yiddish translations, and the Rema cites it constantly in his glosses on the Shulchan Aruch and in Darchei Moshe as the received minhag of Ashkenaz. Through it spread minhagim that Ashkenazim keep to this day: Tashlich, the Purim seudah held mostly by day after Minchah, omitting Tachanun on Lag BaOmer and Tu B’Av, and blowing shofar through the month of Elul except on erev Rosh Hashanah.