ISAAC (middle of the second century), tanna. He is not mentioned in the Mishnah but is often cited in beraitot, especially those dealing with halakhic exegesis in the Talmuds, and in the halakhic Midrashim of the school of R. Ishmael: Mekhilta, Sifrei Numbers, and Sifrei Deuteronomy. It appears that he was a Babylonian, and if so he was one of the earliest known tannaim hailing from Babylonia. During the period of persecution following the Bar Kokhba War, when Hananiah, the nephew of R. Joshua b. Hananiah, attempted to proclaim leap years and to sanctify new moons in Babylonia, and thereby make Babylonia independent of Ereẓ Israel, Rabbi (the nasi at the time, perhaps *Simeon b. Gamaliel) sent him "three communications through R. Isaac and R. Nathan" so as to restrain the Diaspora from taking this step (tj, Sanh. 1:2). Isaac moved to Ereẓ Israel, where he debated halakhic matters, particularly with the disciples of R. Ishmael. He also associated with R. *Simeon b. Yoḥai (Gen. R. 35:16), and engaged in dispute with Judah ha-Nasi and others (Ber. 48b, Git. 27b, etc.). Among his expositions of biblical verses some are of an aggadic character: "Remember the Sabbath day, i.e., count not [the days of the week] as others count them, but count them with reference to the Sabbath" (Mekh., Jethro, 7). He also engaged in mystical studies (Ḥag. 13a).
Bacher, Tann; Hyman, Toledot, 78ff.; Epstein, Tanna'im, 570.
[Zvi Kaplan and
"Isaac." Encyclopaedia Judaica. . Encyclopedia.com. (August 15, 2018). http://www.encyclopedia.com/religion/encyclopedias-almanacs-transcripts-and-maps/isaac-1
"Isaac." Encyclopaedia Judaica. . Retrieved August 15, 2018 from Encyclopedia.com: http://www.encyclopedia.com/religion/encyclopedias-almanacs-transcripts-and-maps/isaac-1