Rabbi Jacob Barukh Landau was the son of Rabbi Judah Landau, one of the most prominent 15th century German rabbis. who had been a student of the Maharil and headed a large Yeshiva. Jacob Baruch was born and educated in Germany. His main teacher in Torah was his father. Early in the second half of the 15th century he emigrated to Italy.
He resided first in Pavia where he composed the treatise Sefer Hazon which features rabbinic riddles. Later he moved to Naples where he served as proofreader in a newly established Hebrew printing press.
Rabbi Jacob Baruch Landau was the author of Sefer Agur, a collection of laws of Orah Hayyim and Yoreh De’ah, in which he cited the different views of the Poskim and stated his own opinion or the accepted practice. He also acquaints us with the decisions and customs of Ashkenazi Jewry’s leading rabbis of his time, such as the Maharil, Rabbi Israel Isserlein, his father Judah Landau and others. Rabbi Jacob Landau was well versed in Kabbalah and his views were influenced by the Zohar and other Kabbalistic books.
The Agur and Sefer Hazon were printed a number of times. Their first edition appeared in Naples circa 1487. A complete edition based on early printings and a manuscript accompanied by notes and source references and an introduction describing Rabbi Jacob Baruch Landau’s life, family and literary activity was published by the late Rabbi Moshe Herschler in 1960 in Jerusalem.
The Agur is often quoted by Rabbi Joseph Caro in his Beth Yosef, by Rabbi Moshe Isserles and by Rabbi Shlomo Luria in his Yam Shel Shlomo and by later Poskim.
The Sefer Hazon is, as mentioned earlier, a collection of rabbinic riddles.
The first riddle reads: How can this be? Two boys, one was born one day before the other. The one who was born after him will reach the Bar Mitzvah age a month before the one who was born before him. The answer: The boys were born in a leap year. One was born on the 29th day of Adar I. The other was born on the first day of Adar II. The year in which they were to celebrate their thirteenth birthday was an ordinary year. The one who was born on the 29th day of Adar I will have to wait until the 29th of Adar of his 13th year to reach religious adulthood. The one, who was born after him, on the first day of Adar II, will enter the age of Mitzvot on the first of Adar of his 13th year.
It is interesting to note that the same riddle and its solution are also found in the responsa of Rabbi Judah Minz, a contemporary of Rabbi Jacob Landau. Like Rabbi Landau, Rabbi Judah Minz, was born in Germany and emigrated to Italy, becoming there rabbi of the community of Paduaa and head of its Yeshiva. He served in both positions for many years until his death in 1506.
In his responsa (Siman 9) Rabbi Minz writes that many, many years ago he was asked how it was possible that Shimeon should become Bar Mitzvah some time before Reuven, who was born before him. The answer is: “Reuven was born at the end of Adar I and Shimeon was born in the beginning of Adar II. Their 13th year was an ordinary year. Therefore Shimeon, who was born in the beginning of Adar II will become Bar Mitzvah on the first day of Adar. Reuven who was born on the 29th day of Adar will become Bar Mitzvah on the 29th day of Adar, i.e. 28 days after Shimeon.”
Rabbi Joseph Caro quotes in his commentary, Beth Yosef on Tur Orah Hayyim, Siman 55, Rabbi Jacob Baruch Landau’s riddle and demonstrates on the basis of the Talmud Arakhin 31b the correctness of the view that boys born in a leap year, in the month of Adar I or Adar II become bar Mitvah in a regular year in the month of Adar.
Rabbi Joseph also incorporated this view in his Shulhan Arukh. In Shulhan Arukh, Orah Hayyim 55,10, we read: If one boy was born in a leap year on the 29th day of Adar I and one boy was born on the first day of Adar II, when the year, in which they reach the age of 13 is an ordinary year, the one who was born on the 29th day of Adar I must wait until the 29th of Adar (of his thirteenth year) to become Bar Mitzvah, and the one who was born after him, on the first day of Adar II, will reach the age of Mitzvot on the first day of Adar.”
Thus the solution of a rabbinic riddle found its way into the Shulhan Arukh.
The Jewish Press, Friday June 4, 2004