The hadith, insofar as they addressed issues not dealt…

““The hadith, insofar as they addressed issues not dealt with in the Quran, would become an indispensable tool in the formation of Islamic law. However, in their earliest stages, the hadith were muddled and totally unregulated, making their authentication almost impossible. Worse, as the first generation of Companions passed on, the community had to rely increasingly on the reports that the second generation of Muslims (known as the Tabiun) had received from the first; when the second generation died, the community was yet another step removed from the actual words and deeds of the Prophet. Thus, with each successive generation, the “chain of transmission,” or isnad, that was supposed to authenticate the hadith grew longer and more convoluted, so that in less than two centuries after Muhammad’s death, there were already some seven hundred thousand hadith being circulated throughout the Muslim lands, the great majority of which were unquestionably fabricated by individuals who sought to legitimize their own particular beliefs and practices by connecting them with the Prophet. After a few generations, almost anything could be given the status of hadith if one simply claimed to trace its transmission back to Muhammad. In fact, the Hungarian scholar Ignaz Goldziher has documented numerous hadith the transmitters of which claimed were derived from Muhammad but which were in reality verses from the Torah and Gospels, bits of rabbinic sayings, ancient Persian maxims, passages of Greek philosophy, Indian proverbs, and even an almost word-for-word reproduction of the Lord’s Prayer. By the ninth century, when Islamic law was being fashioned, there were so many false hadith circulating through the community that Muslim legal scholars somewhat whimsically classified them into two categories: lies told for material gain and lies told for ideological advantage. In””

— Reza Aslan