Although a commentary on a text is, by definition, secondary to the master text it seeks to illuminate, Rashi's commentary to the Torah became an almost independent and indispensable work in its own right. Since its publication in the late 15th century, hardly an edition of the Hebrew Bible for Jewish study has appeared without it.

His commentary on the Pentateuch is the first known Hebrew work to have been printed (Italy, 1475). The first Hebrew text of the Pentateuch, printed in 1482, was accompanied by Rashi's commentary. No other commentary on the Hebrew Scriptures in any language has attained comparable recognition, acceptance, and wide geographic distribution, or ever been equaled it in its profound impact on human lives. Over two hundred supercommentaries have been written on his Pentateuch commentary, some even by such distinguished (16th century) halakhists as Joseph Caro, author of the Shulhan Arukh and Elijah Mizrahi.

Rashi's commentary on the Bible, and particularly that on the Pentateuch, also influenced Christian translations in the vernacular. Several important Christian Hebraists exhibited considerable knowledge of Rashi's exegesis. The Franciscan monk and biblical exegete Nicholas de Lyra (1270-1349) studied Rashi's commentaries in the original, and was large responsible for disseminating them among Christian Hebraists.

His Postillae, a fifty-volume work of vast erudition that became the most widely used and most influential of all medieval Latin commentaries on the Bible (first published in Rome in 1471-72), drew heavily on Rashi's commentaries to the Pentateuch. Nicholas of Lyra wrote in the Introduction to his Postillae: ". . . I intend, for making clear the literal sense, to introduce, not only the statements of the Catholic doctors, but also of the Hebrews, especially of Rabbi Solomon who, among the Hebrew doctors, has spoken most reasonably."

When Martin Luther (1483-1546), leader of the German Protestant Reformation, translated the Latin Bible into the German vernacular so as to place it into the hands of ordinary Christians, he relied heavily on Nicholas of Lyra and incorporated Rashi's interpretations into his own version. Four later Latin translations that appeared in the sixteenth century all utilized Rashi. Thus the translators of the classic English rendering known as the King James Version made abundant use of Rashi directly from the original Hebrew, indirectly from Latin versions, and from the earlier Christian Hebraists.

In writing his commentaries, Rashi sought the best way to pass on the heritage of the Bible and Talmud to a Jewish society that was trying to adapt to a new and different environment. He struggled with the same issue that the Sadduccees and Pharisees had disputed centuries earlier: whether Scripture should be given a literal meaning or interpreted according to spirit of the word. Rashi, with a feel for the times, sensed that a literal interpretation of the law would make the Torah dogmatic and spiritless; he also understood that a free interpretation ran the risk of encouraging far-fetched allegory and mysticism.

Rashi strove for simplicity in his commentaries. He achieved a unique blending of peshat (plain meaning) and derash (homiletical, related to the word midrash); "Let the interpreter keep interpreting, but we are interested in the simple natural meaning of the text," he wrote. Rashi quoted Talmudic interpretations but also felt free to ignore or explicitly reject them when necessary. His commentaries are rich in midrashic references offering readers an introduction into the world of rabbinic folklore. Some three-quarters of Rashi's comments are drawn from classical rabbinic literature, including the Targums, homiletical and halakhic midrash, in addition to the Babylonian Talmud.

So as to make his commentary as understandable as possible, Rashi took the liberty of augmenting or abridging a midrash. On occasion he even altered the wording to adapt the language of the midrash to that of the text. His commentaries also reflect his extraordinary penchant, almost unique for the Middle Ages, for explaining the realia of life in biblical and talmudic times. A keen observer of nature and of human activities, he incorpoated much of what he had learned from the cosmopolitan and commercial atmosphere that pervaded the regions of Troyes, Worms and Mainz where he grew up and studied.

Rashi's work reflect his innate modesty and singular humility of the man. Writes Sarna: "When the resources at his disposal left him unsatisfied as to the true meaning of a word or phrase, he was not ashamed to admit ignorance. His writings are spiced with such comments as 'I am unable to explain it' or 'I do not know what it teaches us' or simply, '"I do not know.' Moreover, he showed no vested interest in his exegesis. He was quite prepared to revise his work in the light of new scholarly research, which came to hand.

He was also quite prepared to admit to having erred in making a certain comment. Thus, in a letter found in the collection of his Responsa he freely states in regard to Ezekiel 40:17: 'I erred in that comment.' Such confessions are practically unparalleled among the great medieval Jewish exegetes and . . . virtually nonexistent among modern scholars. Rashi was not only a nondogmatic seeker of the truth, but he displayed intellectual honesty and scholarly integrity."

Rashi's commentaries on most of the tractates of the Talmud have been preserved. His commentary to Bava Batra was completed by his grandson and pupil, Samuel b. Meir (Rashbam), and to Makkot by his pupil, Judah b. Nathan.

Rashi's explanations of words are often colorful, his commentary replete with realistic, concrete descriptions. He adduces reasons for halakhot (religious rulings) and talmudic argumentations, often providing psychological and realistic backgrounds to talmudic times. With an excellent feeling for the methodology of the Talmud, he points out difficulties in the construction of the passages and unusual terminology. At times his language can be terse due to his assuming that the reader is fully acquainted with all the relevant details. Generally, Rashi did not state his sources but these have been given in detail by Zunz in his book on Rashi.

Rashi's commentary to the Talmud was published with the first printed edition of the Talmud, and except for modern editions of a few tractates, no edition of the Talmud has appeared without it. His commentaries on most of the tractates of the Talmud have been preserved.

His commentary to Bava Batra was completed by his grandson and pupil, Samuel b. Meir (Rashbam), and to Makkot by his pupil, Judah b. Nathan. Rashi did not write commentaries to those tractates that have no Babylonian Talmud. Many scholars agree that the commentaries on tractates Avot , Ta'anit, Nedarim, Nazir, and Horayot ascribed to him are not his.