The Mekhilta of Rabbi Ishmael (Aramaic: IPA /m?'?il/, "a collection of rules of interpretation") is midrash halakha to the Book of Exodus. The Jewish Babylonian Aramaic title Mekhilta corresponds to the Mishnaic Hebrew term middah "measure," "rule", and is used to denote a compilation of exegesis (? middot; compare talmudical hermeneutics).
Neither the Babylonian Talmud nor the Jerusalem Talmud mention this work under the name "Mekhilta," nor does the word appear in any of the passages of the Talmud in which the other halakhic midrashim, Sifra and Sifre, are named. It seems to be intended, however, in one passage which runs as follows: "R. Josiah showed a Mekhilta from which he cited and explained a sentence." The text quoted by R. Josiah can be found in the extant version of the Mekhilta, Mishpatim.
On the other hand, this midrash, apparently in written form, is mentioned several times in the Talmud under the title She'ar Sifre debe Rav "The Other Books of the Schoolhouse". A geonic responsum in which appears a passage from the Mekhilta likewise indicates that this work was known as She'ar Sifre debe Rav. The first individual to mention the Mekhilta by name was the author of the Halakhot Gedolot.
Another geonic responsum refers to the text as the Mekhilta d?Ere? Yisrael, probably to distinguish it from the Mekhilta of Rabbi Shimon bar Yochai, which was generally known in the Babylonian schools.
The author or redactor of the Mekhilta cannot be definitely ascertained. Nissim ben Jacob and Samuel ibn Naghrillah refer to it as the Mekhilta de-Rabbi Yishmael, thus ascribing the authorship to Ishmael. Maimonides likewise says: "R. Ishmael interpreted from 've'eleh shemot' to the end of the Torah, and this explanation is called 'Mekhilta.' R. Akiva also wrote a Mekhilta." This Ishmael, however, is neither an amora by the name of Ishmael as Zecharias Frankel assumed, nor Judah ha-Nasi's contemporary, Ishmael ben Jose, as Gedaliah ibn Ya?ya thought. He is, on the contrary, Ishmael ben Elisha, Rabbi Akiva's contemporary, as is shown by the passage of Maimonides quoted above.
The present Mekhilta cannot, however, be the one composed by Ishmael, as is proved by the references in it to Ishmael's pupils and to other later tannaim. Both Maimonides and the author of the Halakhot Gedolot, moreover, refer, evidently on the basis of a tradition, to a much larger Mekhilta extending from Exodus 1 to the end of the Torah, while the midrash here considered discusses only certain passages of Exodus. It must be assumed, therefore, that Ishmael composed an explanatory midrash to the last four books of the Torah, and that his pupils amplified it.
A later editor, intending to compile a halakhic midrash to Exodus, took Ishmael's work on the book, beginning with ch. 12, since the first eleven chapters contained no references to the halakhah. He even omitted passages from the portion which he took, but (by way of compensation) incorporated much material from the other halakhic midrashim, Sifra, the Mekhilta of Rabbi Shimon, and the Sifre to Deuteronomy. Since the last two works were from a different source, he generally designated them by the introductory phrase, "davar a?er" = "another explanation," placing them after the sections taken from Ishmael's midrash. But the redactor based his work on the midrash of Ishmael's school, and the sentences of Ishmael and his pupils constitute the larger part of his Mekhilta. Similarly, most of the anonymous maxims in the work were derived from the same source, so that it also was known as the "Mekhilta of Rabbi Ishmael." The redactor must have been a pupil of Judah ha-Nasi, since the latter is frequently mentioned.
He cannot, however, have been Hoshaiah, as Abraham Epstein assumes, as might be inferred from Abraham ibn Daud's reference, for Hoshaiah is mentioned in the Mekhilta. Abba Arika therefore probably redacted the work, as Menahem ibn Zerah says. Abba Arika however, did not do this in Babylonia, as Isaac Hirsch Weiss assumes, but in Palestine, taking it after its compilation to Babylonia, so that it was called "Mekhilta de-Eretz Yisrael".
Barayata from the Mekhilta are introduced in the Babylonian Talmud by the phrases Tana debe R. Yishmael ("It was taught in the school of R. Ishmael"), and in the Jerusalem Talmud and the aggadahs by Teni R. Yishmael ("R. Ishmael taught"). Yet there are many barayata in the Talmud which contain comments on Book of Exodus introduced by the phrase Tana debe R. Yishmael but which are not included in the Mekhilta under discussion. These must have been included in Ishmael's original Mekhilta, and the fact that they are omitted in this midrash is evidence that its redactor excluded many of the passages from Ishmael's work.
The Mekhilta begins with Exodus 12, this being the first legal section found in Exodus. That this is the beginning of the Mekhilta is shown by the Arukh s.v. , and by the Seder Tannaim v'Amoraim. In like manner, R. Nissim proves that the conclusion of the Mekhilta which he knew corresponded with that of the Mekhilta now extant. In printed editions the Mekhilta is divided into nine "massektot," each of which is further subdivided into "parshiyyot". The nine massektot are as follows:
The Mekhilta comprises altogether 77, or, if the two introductions be included, 79 sections. All the editions, however, state at the end that there are 82 sections.
Although the redactor intended to produce a halachic midrash to Book of Exodus, the majority of the Mekhilta is aggadic in character. From Exodus 12 the midrash was continued without interruption as far as Exodus 33:19, i.e. to the conclusion of the chief laws of the book, although there are many narrative portions scattered through this section whose midrash belongs properly to the aggadah. Furthermore, many aggadot are included in the legal sections as well.
The halakhic exegesis of the Mekhilta, which is found chiefly in the massektot "Bo", "Bahodesh", and "Mishpatim" and in the sections "Ki Tisa" and "Vayakhel", is, as the name "mekhilta" indicates, based on the application of the middot according to R. Ishmael's system and method of teaching. In like manner, the introductory formulas and the technical terms are borrowed from his midrash. On the other hand, there are many explanations and expositions of the Law which follow the simpler methods of exegesis found in the earlier halakha.
The aggadic expositions in the Mekhilta, which are found chiefly in "Beshallah" and "Yitro" are in part actual exegesis, but the majority of them are merely interpretations of Scripture to illustrate certain ethical and moral tenets. Parables are frequently introduced in connection with these interpretations  as well as proverbs and maxims. Especially noteworthy are the aggadot relating to the battles of the Ephraimites and to Serah, Asher's daughter, who showed Joseph's coffin to Moses, besides others, which are based on old tales and legends.
Some of the tannaim mentioned in the Mekhilta are referred to only here and in Sifre Numbers, which likewise originated with R. Ishmael's school. On the earlier editions of the Mekhilta and the commentaries to it see I.H. Weiss and M. Friedmann.