Shimon bar Yochai (Zoharic Aramaic: שמעון בר יוחאי, Šimʿon bar Yoḥay) or Shimon ben Yochai (Mishnaic Hebrew: שמעון בן יוחאי),[note 1] also known by the acronym Rashbi,[note 2] was a 2nd-century tanna or sage of the period of Roman Judaea and early Syria Palaestina.

The Zohar, a 13th-century foundational work of Kabbalah, is ascribed to him by Kabbalistic tradition, but this claim is universally rejected by modern scholars.

An 8th-century pseudonymous attribution of divine revelations to Shimon by the angel Metatron is also known, called The Secrets of Rabbi Simon ben Yohai.

[3] Berakhot 28a relates that Shimon had previously studied at Yavne, under Gamaliel II and Joshua ben Hananiah, and that he was the cause of the infamous quarrel that broke out between these two leaders.

However, this statement is somewhat chronologically difficult, considering that about forty-five years later, when Akiva was thrown into prison, Shimon's father was still alive.

Conscious of his merit, Shimon felt hurt at being ranked after Meir, and Aqiva was compelled to soothe him with soft words.

During Akiva's lifetime, Shimon was occasionally found at Sidon, where he seems to have shown great independence in his halakhic decisions.

The following incident is recorded, illustrating his wit and piety: A man and his wife, childless despite ten years of marriage, appeared before Shimon at Sidon to secure a divorce.

Shimon was compelled to seek refuge in a cavern, where he remained for thirteen years till the emperor, possibly Antoninus Pius, who reigned until 161, died.

[9] Shimon, accompanied by his son Eleazar, hid in a cavern near Gadara, where they stayed for thirteen years, living on dates and carob fruit.

Resolving to remove the cause of the uncleanness, Shimon planted lupines in all suspected places; wherever they did not take root, he knew that a tomb was underneath.

[17] As the last significant event in Shimon's life, it is said that he was sent to Rome (accompanied by Eleazar ben Jose) with a petition to the emperor for the abolition of the decree against the three Jewish observances and that his mission was successful.

Israel Lévi[20] thinks it is a variation of the legend of the apostle Bartholomew exorcising a demon that had taken possession of the daughter of Polymnius, the King of India.

[22] Bacher thinks there is another Christian legend which corresponds more closely to the Talmudic narrative: that in which Abercius exorcised a demon from Lucilla, the daughter of Marcus Aurelius.

[26] Thus, on account of his exceptional piety and continual study of the Law, Shimon was considered as one of those whose merit preserves the world, and therefore during his life the rainbow was never seen, that promise of God's forbearance not being needed.

Shimon's halakhot are very numerous; they appear in every tractate of the Talmud except Berakhot, Hallah, Ta'anit, Nedarim, Tamid, and Middot.

The particular characteristic of Shimon's teaching was that whether in a halakhah or in a aggadic interpretation of a Biblical command, he endeavored to find the underlying reason for it.

[34] Shimon's name was widely identified with this halakhic principle of interpretation, and his teacher Akiva approved of it; therefore his contemporaries often applied to him when they wished to know the reason for certain halakhot.

[40] He differed from Akiva in that he did not think that particles like "et," "gam," and others contain in themselves indications of halakhot;[41] but in many instances he showed that he was opposed to Ishmael's opinion that the Torah speaks as men do and that seemingly pleonastic words can never serve as the basis for deducing new laws.

[50] His animosity toward the Gentiles generally and toward feminine superstition is expressed in the following utterance: "The best of the heathen merits death; the best of serpents should have its head crushed; and the most pious of women is prone to sorcery.

"[51] Although often quoted by antisemites,[52] his comment was uttered after witnessing his teacher being tortured to death,[53] bar Yochai himself becoming a fugitive after speaking out against Roman oppression.

[54] His hostility to the Romans is expressed also in his maxims; thus, alluding probably to the Parthian war which broke out in the time of Antoninus Pius, he said: "If you see a Persian horse tied to [the graves of][a]Israel, look for the steps[b] of the Messiah".

There exist two apocryphal midrashim ascribed to Shimon:[59] "The Secrets of Rabbi Simon ben Yohai" and "Tefillat R. Shim'on b. Yoḥai".

The main point of these midrashim is that while Shimon was hidden in the cavern, he fasted forty days and prayed to God to rescue Israel from such persecutions.

While he was originally attributed authorship of the Zohar, this claim is universally rejected by modern scholars, who point to Moses de León as the primary author.

Some believe that bar Yochai died on the 33rd day of the Omer, known as Lag BaOmer, due to a printing error in Hayyim Vital's Pri Etz Chadash.

It is popularly believed that if one donates or offers 18 rotels of liquid refreshment (grape juice, wine, soda or even water) to those attending the celebrations at bar Yochai's tomb on Lag BaOmer, then the giver will be granted miraculous salvation.