Isaac Seligman Baer (1825–1897) was a Hebrew grammarian, masorah scholar, and liturgist. Born at Mosbach, Baer was a pupil of Wolf Heidenheim, who left him many of his manuscripts. At the age of 19 he turned to masoretic studies. Franz Delitzsch was impressed by Baer's scholarly approach and together they published the Psalms with masorah (1860) followed by most of the other books of the Bible with masorah texts. Delitzsch prefaced each book with a Latin introduction (except the two which appeared after his death, i.e., Jeremiah in 1890 and Kings in 1895). These masoretic editions were compiled by Baer from manuscripts representing the variants of the masorah of Ben Asher, Ben Naphtali, and other masorah texts. All his life, Baer remained in the humble position of a teacher in the Jewish community school at Biebrich (Rhineland), but on the initiative of Delitzsch he was awarded an honorary Ph.D. by the University of Leipzig (1876). Baer's masoretic Bible edition was generally regarded as a genuine rendition of the traditional masorah text although it also evoked some criticism.. Baer's masorah text was printed in the widely accepted Vilna edition of the rabbinic Bible (Mikra'ot Gedolot). He also wrote a book on the cantillation in the poetical books of the Bible (Torat Emet, 1852) and on the secondary accent, the meteg (Die Methegsetzung, 1867); and published Ben Asher's Dikdukei Te'amim (1879) and Zwei alte Thorarollen aus Arabien (1870).

Baer's greatest achievement lay in the field of liturgy. His many editions of liturgical texts were not only a scholarly feat but added dignity and decorum to Orthodox synagogue services throughout Western Europe, where his editions gained great popularity. The most important of these is his Avodat Yisrael prayer book with a scholarly commentary Yakhin Lashon (1868). Besides this major work, Baer edited: Selihot, Kinot, Seder ha-Berakhot (1858), a handbook for mourners, cemetery use, etc., in three versions (Toze'ot Hayyim, 1862; Sefer Gemilut Hasadim, 1880; Derekh la-Hayyim, 1926); Tikkun ha-Sofer ve-ha-Kore, a handbook for scribes and readers of the Torah (1875); a prayer book Tefillat Yesharim (1876, with prayers in German at the end; these also appeared separately as Kol Bat Ziyyon, 1875); Piyyutim (1874); Divrei ha-Berit, circumcision service (1874).