Anan Ben David (Hebrew: ענן בן דוד, c. 715 - c. 795) is widely considered to be a major founder of Karaite Judaism.
From the second third of the 7th century and until middle of the 8th, as a result of the tremendous intellectual commotion produced throughout the West Asia by the swift early Muslim conquests and the collision of Islam with the religions and cultures of the world, there arose a large number of religious sects, especially in Persia, Iraq, and Syria.
Some polemical accounts supply Anan with a typical background story often used of "heretics"—namely, that he was frustrated in a bid for power within the religious community and as a result broke away.
Eventually, Josiah was elected exilarch by the geonim or leaders of the Talmudic academies in Babylonia and by the notables of the chief Jewish congregations.
Luckily for Anan, the story goes, he met in jail a prominent fellow prisoner, the founder of the Hanafi school of Islam, Abu Hanifah.
He gave Anan advice which saved his life: He should set himself to expound all ambiguous precepts of the Torah in a fashion opposed to the traditional interpretation and make this principle the foundation of a new religious sect.
Moreover, Leon Nemoy notes, "Natronai, scarcely ninety years after Anan's secession, tells us nothing about his aristocratic (Davidic) descent or about the contest for the office of exilarch which allegedly served as the immediate cause of his apostasy."
(See Karaite Anthology; Yale Judaica Series 7) Anan ben David's Sefer ha-Miṣwot or "Book of the Precepts" was published about 770.
This doctrine, represented in Greek antiquity especially by Empedocles and the Pythagoreans, had always been widespread in India, and even though it was found among some Muslim sects, such as the followers of ibn al-Rawandi, it was also a central tenet of Manichaeism, which was enjoying something of a renaissance in the region at the time of Anan.
Unleavened bread (Maẓẓah) must be made exclusively of barley-meal, and he that prepares it out of wheaten meal incurs the punishment appointed for those that eat actual leaven (ḥameẓ).
Anan ben David, in direct contradiction of Karaites such as Daniel Al-Kumisi, had small respect for science as is often shown in his law-book.
His opposition to the astronomical determination of the festivals, of which he boasted to the caliph, led him to declare astronomy as a branch of the astrology and divination forbidden in the Bible, thus undermining the very foundation of the rabbinical calendar.