Jewish myths in Muslim traditions

In answer to the video "How Islam Shaped Its Sources"

The type of hadith classified as israeliyyat are Jewish myths, used by story-tellers, who would include them in their narrations. They wanted to answer the popular sense of curiosity in trivial, spiritually inconsequential details in the lives and times of former prophets. These israeliyyat were mainly written by the early converts from the people of the book. With Islam's fast advance throughout the Judeo-Christian communities of the Middle East, it is obvious that these converts would not at once totally free their minds from their previous religious tradition. Many continued to explain the Quranic narratives using their Biblical information. Under Abubakr's caliphate for instance, Abdullah bin ‘Amr bin ‘Aas, an ex-Jew took possession of many books gathered by the Byzantine Christians following the battle of Yarmouk, and he would use the information therein to comment on certain Quran passages and disseminated many of the stories among the Muslims, which would be used by later commentators. The technical term itself was not used systematically before Ibn Kathir. Although before him, the Andalusian exegete, Abu bakr Ibn al-Arabi mentioned it. Ibn Taymiyya, the mentor of Ibn Kathir, and Ibn Taymiyya's contemporary al-Tufi discussed israeliyyat before Ibn Kathir. Keeping in mind the existence of so many published and unpublished tafsirs, it is virtually impossible to identify the commentator who was the first user of the term israeliyyat in a technical sense. These reports have been always understood as an amalgam of truth and falsehood. 

The Muslim story tellers would take for basis the Quranic text, then add the Jewish traditions from the converts where they deemed it most fit, resulting in a commentary that is neither Quranic nor Jewish. Although Muslims in their exegetical and non-exegetical works tried as much as possible to keep them out of their works on the Quran, they were not always successful in that endeavour. Muslim scholars since Tabari, ibn Atiyya, al Khazin, ibn al Jawzi etc all spoke of these traditions with various ethnic terms evoking their Judeo-Christian origins "the claims of the people of the scriptures", or "what the historians of the people of the book invent" etc. The prophet himself was alert to the potential intrusions of Jewish traditions in the minds of his followers. Umar once asked a Jew from Medina to copy for him sections of the Torah, and when it was presented to the prophet "his countenance changed then he said to Umar;

"Were Moses to appear in your midst and were you then to follow him and abandon me, you would go astray. Of all peoples, you are my lot; just as of all the prophets I am your lot"