Polemical correspondence against Shabbethai Zevi and his followers, abridged and published under the title "Kitzur Tzitzat Novel Zvi" by R. Jacob Emden.

R. Jacob ben Aaron Sasportas (1610 – April 15, 1698), was a Rabbi, Kabbalist, and anti-Shabbethaian. R.Sasportas was born at Oran. He became rabbi successively of Tlemcen (at the age of twenty-four), Marrakesh, Fes, and Salé. In about 1646 he was imprisoned by the Moorish king, but succeeded in escaping with his family to Amsterdam (ca. 1653). He stayed there till the disorders in Africa ceased, when he was called back by the King of Morocco and sent on a special mission to the Spanish court (ca. 1659) to ask for aid against the rebels. On his return he was invited to the rabbinate of the Portuguese community of London (1664). According to David Franco Mendes (in "Ha-Meassef," 1788, p. 169), Jacob had accompanied Menasseh ben Israel to London in 1655. Owing to the outbreak of the plague in London in 1665, Jacob went to Hamburg, where he officiated as rabbi till 1673. In that year he was called to Amsterdam and appointed head of the yeshivah Keter Torah, founded by the brothers Pinto. Two years later he became dayyan and head of the yeshivah at Leghorn (Livorno), and in 1680 he returned to Amsterdam, where he was appointed head of the yeshivah 'Eitz Hayyim. After the death of R. Isaac Aboab da Fonseca (1693) he was appointed rabbi of the Portuguese community, which office he held till his death at Amsterdam.

R. Jacob was one of the most violent antagonists of the Shabbethaian movement; he wrote many letters to various communities in Europe, Asia, and Africa, exhorting them to unmask the impostors and to warn the people against them. He wrote Tzitzat Novel Zvi (ib. 1737), polemical correspondence against Shabbethai Zevi and his followers, also edited by his son.

R. Jacob Emden (pen name Yavez; derived from Ya'akov Ben Zevi; 1697–1776), rabbi, halakhic authority, kabbalist, and anti-Shabbatean polemicist. Emden was regarded as one of the outstanding scholars of his generation. Emden's teacher was his father R. Zevi Hirsch Ashkenazi (Hakham Zevi). He inherited his father's interest in secular studies, his dissociation from the Ashkenazi method of study (pilpul) and customs, his stormy, independent, and uncompromising character, and his devotion to the campaign against the Shabbateans and their sympathizers. In addition, he possessed a fine literary talent, a critical tendency and a knowledge unusual for his age of general non-halakhic Jewish literature. He was also familiar with sciences and languages (German, Dutch, Latin). Despite his distinguished descent and his remarkable talmudic attainments, R. Emden occupied no official position, with the exception of a few years as rabbi of Emden (1728–1733). This made it possible for him to be exceptionally critical toward the society and the tradition of his time. He was more on guard about anything that he considered hillul ha-Shem (bringing the name of the Jew into disrepute) than for the good name of the rabbinate and of the community. He made extensive use of the private printing press he founded in Altona to disseminate his views. As a result, because of his views on a number of issues, both personal and communal, he became a figure widely respected, feared, and contentious.

His historical importance includes his campaigns against the Shabbateans to which he dedicated many years. He relentlessly examined and investigated every suspicious phenomenon pertaining to the sect. He called upon the contemporary rabbis to publish excommunications and mercilessly attacked anyone suspected of supporting or showing sympathy to the Shabbateans. The Shabbateans were accustomed to introduce hints of their secret doctrine into their literary works, particularly in the field of Kabbalah. Consequently, R. Emden became an expert in uncovering such allusions and hidden meanings, and developed an extraordinarily sharp critical faculty by which he could recognize any suggestion of the Shabbatean heresy. Many books in which no one saw anything to which objection could be taken, were condemned by him as heretical. Though at times he was at fault and suspected the innocent without cause, his judgment in general was sound.

Shabbetai Tzevi, also spelled Sabbatai Zebi or Sabbatai Zevi, (born July 23, 1626, Smyrna, Ottoman Empire [now İzmir, Turkey]—died 1676, Ulcinj, Ottoman Empire [now in Montenegro]), a false messiah who developed a mass following and threatened rabbinical authority in Europe and the Middle East. As a young man, Shabbetai steeped himself in the influential body of Jewish mystical writings known as the Kabbala. His extended periods of ecstasy and his strong personality combined to attract many disciples, and at the age of 22 he proclaimed himself the messiah. Driven from Smyrna by the aroused rabbinate, he journeyed to Salonika (now Thessaloníki), an old Kabbalistic centre, and then to Constantinople (now Istanbul). There he encountered an esteemed and forceful Jewish preacher and Kabbalist, Abraham ha-Yakini, who possessed a false prophetic document affirming that Shabbetai was the messiah. Shabbetai then traveled to Palestine and after that to Cairo, where he won over to his cause Raphael Halebi, the wealthy and powerful treasurer of the Turkish governor. With a retinue of believers and assured of financial backing, Shabbetai triumphantly returned to Jerusalem. There, a 20-year-old student known as Nathan of Gaza assumed the role of a modern Elijah, in his traditional role of forerunner of the messiah. Nathan ecstatically prophesied the imminent restoration of Israel and world salvation through the bloodless victory of Shabbetai, riding on a lion with a seven-headed dragon in his jaws. In accordance with millenarian belief, he cited 1666 as the apocalyptic year. Threatened with excommunication by the rabbis of Jerusalem, Shabbetai returned to Smyrna in the autumn of 1665, where he was wildly acclaimed. His movement spread to Venice, Amsterdam, Hamburg, London, and several other European and North African cities.

At the beginning of 1666, Shabbetai went to Constantinople and was imprisoned on his arrival. After a few months, he was transferred to the castle at Abydos, which became known to his followers as Migdal Oz, the Tower of Strength. In September, however, he was brought before the sultan in Adrianople and, having been previously threatened with torture, became converted to Islam. The placated sultan renamed him Mehmed Efendi, appointed him his personal doorkeeper, and provided him with a generous allowance. All but his most faithful or self-seeking disciples were disillusioned by his apostasy. Eventually, Shabbetai fell out of favour and was banished, dying in Albania. The movement that developed around Shabbetai Tzevi became known as Shabbetaianism. It attempted to reconcile Shabbetai’s grandiose claims of spiritual authority with his subsequent seeming betrayal of the Jewish faith. Faithful Shabbetaians interpreted Shabbetai’s apostasy as a step toward ultimate fulfillment of his messiahship and attempted to follow their leader’s example. They argued that such outward acts were irrelevant as long as one remains inwardly a Jew. Those who embraced the theory of “sacred sin” believed that the Torah could be fulfilled only by amoral acts representing its seeming annulment. Others felt they could remain faithful Shabbetaians without having to apostatize. After Shabbetai’s death in 1676, the sect continued to flourish. The nihilistic tendencies of Shabbetaianism reached a peak in the 18th century with Jacob Frank, whose followers reputedly sought redemption through orgies at mystical festivals.