In the Bible
The first recorded reference to apostasy from Judaism is in Deuteronomy 13:6-11, which states:
If your very own brother, or your son or daughter, or the wife you love, or your closest friend secretly entices you, saying, "Let us go and worship other gods" (gods that neither you nor your fathers have known, gods of the peoples around you, whether near or far, from one end of the land to the other), do not yield to him or listen to him. Show him no pity. Do not spare him or shield him. You must certainly put him to death. Your hand must be the first in putting him to death, and then the hands of all the people. Stone him to death, because he tried to turn you away from the LORD your God, who brought you out of Egypt, out of the land of slavery. Then all Israel will hear and be afraid, and no one among you will do such an evil thing again.
In the Talmud
In the Talmud, Elisha ben Abuyah (referred to as Acher, the "Other One") is singled out as an apostate by the rabbis.
In Medieval Spain, a systematic conversion of Jews to Christianity took place, largely under threats and force. The apostasy of these conversos provoked the indignation of some Jews in Spain and it was made illegal to call a converso by the epithet tornadizo (renegade).
Several inquisitors of the Spanish Inquisition, such as Tomás de Torquemada, and Francisco Quiñones the Bishop of Coria, are thought to be descendants of apostate Jews. Known apostates who made their mark in history by attempting to convert other Jews in the 14th and 15th centuries include Juan de Valladolid and Astruc Remoch.
Some Spanish Jews, however, remained crypto-Jews despite being compelled to convert to Christianity (see Anusim). They are also called Marranos.
Sabbatai Zevi and Jacob Frank
In 1648 Sabbatai Zevi claimed to be the Jewish Messiah. His Jewish followers were known as Sabbateans. Zevi converted to Islam in 1666. Afterwards, some of his followers willingly converted but continued to practise Sabbatean rituals. These people became known as the Dönmeh.
In the 1750s Jacob Frank claimed he was the reincarnation of Zevi and attracted many followers in Poland, known as Frankists. In 1759, with Frank's encouragement, more than 500 Frankists were baptized as Catholics. Frank himself was also baptized, with the King of Poland as his godfather.