Abd Allah Ibn Ibad was a khawarij and theoretically the founder of the Ibadite sect in Islam (Today mostly in Oman). In 76 A.H (695) he wrote two letters to the Caliph Abs al-Malik. Despite the fact that Cook in his book “Early Muslim Dogma” disagrees about the authorship and the date of the Letters, we can say for sure that these Letters have originated either in the first century A.H. or the mid-second century. Two Quotes in these Letters are of great importance:

“They abandoned the judgment of their Lord and took hadiths for their religion; and they claim that they have obtained knowledge other than from the Koran…” (Michael Cook, Muslim Dogma, Cambridge, 1981, p. 9)

“They believed in a book which was not from God, written by the hands of men; they then attributed it to the Messenger of God” (Michael Cook, Muslim Dogma, Cambridge, 1981, p. 9)

References: Aisha Musa, “Hadith as scripture”

Michael Cook, “Early Muslim Dogma”