יצחק בן אברהם

Rav Yitzchak ben Avraham of Sens, known as the Rizba and also as the Ri HaBachur, was among the important baalei Tosafot of the twelfth century and the successor of the Ri HaZaken at the head of the yeshiva of Dampierre. He was born in France to Rav Avraham HeChasid of Sens, a well-known nadiv, and was the elder brother of Rav Shimshon of Sens, the Rash miShantz; the two brothers honored one another greatly and consulted each other in psak all their lives. In their youth the brothers learned in Troyes under Rabbeinu Tam, their grandmother’s brother, until his passing, then moved to the yeshiva of the Ri HaZaken at Dampierre, where they were among the greatest talmidim, and the Ri was their rebbe muvhak. After the Ri’s passing the Rizba filled his place at Dampierre while his brother returned to Sens, and he was called Ri HaBachur, the younger, to set him apart from his rebbe the Ri HaZaken.

The Rizba was known for his vast bekiut and his hatmadah: the Mordechai relates of a halachah whose source was said to be in the Yerushalmi that “Rav Yitzchak ben Avraham checked through all of it and did not find it,” and his talmidim told of his custom to rise before dawn to learn. When the Ramah, Rav Meir ben Todros Abulafia, sent his exchange of letters with the chachamim of Lunel concerning the Rambam’s words on techiyat hameitim to the Rizba and his brother to rule in the matter, calling them the two pillars on which the house of wisdom rests; and the Ramban writes that in his teshuvot on the mitzvot that depend on Eretz Yisrael the Rizba drew proofs from the Rambam’s sefarim “and mentions the name of the Rav for praise and for glory.”

He wrote tosafot on the Shas, later abridged into the collections printed on the Gemara — his words appear throughout the printed Tosafot, above all in Tosafot Tuch — along with a work on the seder of leil Pesach, teshuvot quoted in the Hagahot Maimoniyot and the Or Zarua, and a table of sixty-one rows for fixing nineteen consecutive years of the Hebrew calendar from a single molad. And where most of the chachamim of France after the Ri gave themselves to expounding their rebbe’s words, the Rizba many times differed with the Ri and set out new shitot of his own.

His talmidim became the poskim of the next generation: Rabbeinu Baruch, author of the Sefer HaTerumah; Rav Natan ben Meir and Rav Yehuda bar Yakar, the rebbeim of the Ramban; Rav Yechiel of Paris; and Rav Yaakov of Chinon, rebbe of Rabbeinu Peretz. He was niftar at Dampierre before his brother went up to Eretz Yisrael, and gedolei France gathered at his levayah, where, on the testimony of a talmid that such had been his wish, he was buried wrapped in a tallit with its tzitzit.