1. Rabbi Jacob ben Meir, who is called Rabeinu Tam (an acronym of his initials) was the grandson of Rashi, and among the greatest of the Baalei Tosfos (French-German scholars from the 11th-14th centuries).
2. His nickname Rabeinu Tam was also reminiscent of the verse: “And Jacob was a wholehearted man, who dwelt in tents” (Genesis 25:27).
3. Rabeinu Tam was born in northern France. One of the three daughters of Rashi, Yocheved, married Rabbi Meir ben Samuel from the city of Ramerupt. R. Meir and Yocheved had three sons: Isaac, Samuel and Jacob. These boys were the first of the Baalei Tosfos (the authors who added their commentary to the Talmud). Their son Jacob, Rabeinu Tam, was the leader of French Jewry and also had a great impact on German Jewry.
4. During the period in which Rabbi Avraham ben Ezra lived in France, he became friends with Rabeinu Tam. In a correspondence to him, he expressed his reverence for him in the title “You are the place of the Holy Temple”.
5. Rabeinu Tam corresponded with other Torah sages of his generation. He was expert in grammar, and in the dispute between Dunash ben Lavrat and Menachem Ben Saruk, Rabeinu Tam supported Menachem and wrote a book “Hachro’ot” against Dunash the son of Lavrat (who wrote the Shabbat piyyut “Dror Yikra”).
6. The commentary of Rabeinu Tam is the foundation of all the Tosfos commentaries to the Talmud. He also wrote the work “Sefer Hayashar”, which is a two-part collection of Talmudic responsa and commentary.
7. In addition, Rabeinu Tam wrote other works on how to write a Torah scroll and divorce documents, and a prayer book which included the laws of prayer, a number of piyyutim and a book of grammar.
8. The Maharshal (Rabbi Solomon Luria) writes that “eighty Baalei Tosfos were together with Rabeinu Tam… each one of which was capable of determining law … and students too numerous to count.” Among his most famous students: Rabbi Yosef Bechor Shor, Rabbi Eliezer of Metz, Rabbi Y. Halavan, and more.
9. The two views of an ancient controversy regarding the order that parchments are put in the Tefillin, are customarily attributed to Rabeinu Tam and his grandfather, Rashi. Until today there is a distinction between the tefillin of Rashi and the tefillin of Rabeinu Tam. Although the custom is to put on the tefillin of Rashi, those who want to act meticulously put on two pairs of tefillin, one after the other or together.
10. Rabeinu Tam was buried together with his brothers and other Baalei Tosfos in the old cemetery in the town of Ramerupt.