Judaism

Judaism is a monotheistic, Semitic religion originating from Old Earth. It was the only religion from Old Earth that survived intact throughout the millennia. At least one Jewish community had survived on Gammu and there was evidence that others existed or had existed on Salusa Secundus and Nework.

This group of Jewish survivors had survived as a secret society, protected and supported by the Bene Gesserit through a pact of both-sided loyalty, though they sometimes felt amused or dismayed by what they thought of as the Bene Gesserit copying them. Eons ago, after the many pogroms following the Commission of Ecumenical Translators and the establishment of the Orange Catholic Ecumenism, they had decided to completely vanish from public view and therefore hid on countless planets, some of which had been settled by no other humans than themselves. They called this practice the complete cover and it was possible for a person to work and live a lifetime beside a Jew without ever suspecting. Still they preserved their age-old practices, though somewhat altered. Their small communities were led by Rabbis but some chosen women practiced the spice agony and were able to absorb and save other people's collective memory, making them virtually wild Reverend Mothers, a fact they had decided to hide from the true Bene Gesserit.

It is notable that the term Kwisatz Haderach is an Anglicized pronunciation of the phrase קפיצת הדרך (kefitzat haderech) which translates as "the shortening of the way” or "the leap of the path" and is used a concept mentioned in Jewish texts as a miraculously rapid transportation between two physical locations. The term is not used in reference to the awaited Jewish Messiah.

Dune encyclopedia
The Dune Encyclopedia mentions several groups or organisations that seem to be of Jewish origin which had sent delegates to the synode which redacted the Orange Catholic Bible: The Diasporic Council of Rabbis, Talimidic Zabur Followers, the Jerusalem Urbanite Citizens of Nework, the Neomaimondist Rabbirate and The Tawrah Collegiate, as well as a number of seemingly mixed-religions such as: The Christian Zionist Pilgrims, The Hasidic Lutherans and the Hasidislamic Union but their exact relation to judaism remains obscure and it is unknown in how far these Jewish or pseudo-Jewish groups differed from the Judaism of Old Terra, though it is stated that of all religions, Judaism had changed the least throughout the millennia.

Discrepancies
The Dune Prequels by Brian Herbert and Kevin J. Anderson imply that the "Complete Cover" happened before the Synode of the Orange catholic bible, however Frank Herbert's mentioning of at least two Jewish groups attending the Synode implies that the Pogroms and the Complete Cover actually happened after the Synode.